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Discussion Starter #601
Hello,

I finally got around to dropping my fuel tank today in pursuit of fixing the gauge sending unit. I knew that it was not a problem with the actual dash gauge because the gauge passed its self test and I could control the gauge needle by inserting a different resistance in the ground wire - a small resistor just under 4 ohms. The gauge has been perpetually stuck at full which corresponds to 90 ohms of resistance. With four ohms of resistance in line, the needle dependably went to near zero for a fuel level. Thusly . . . bad or stuck sending unit arm.

I had tested the sending unit float arm through its arc and resistance range before installing it last year and measured 0-93 ohms if I remember correctly - close enough to the specification of 0-90 ohms. So it's got to be stuck with the arm somewhere near the top of the tank. Its definitely not a sunk float.

I siphoned out a good amount of gas until I could not siphon out any more and wrestled the tank to the shop floor. The sending unit will come out very soon and we shall see what I've got and then I'll heft it back up and in. This job has been a long time in the making and it'll be good to set things right.

Rick
 

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Discussion Starter #602
Hello,

I gave up on continuing to use the less expensive sending unit with the float ball arm in favor of the more expensive "arm-less" cylindrical sending unit. The cylinder style of sending unit is 98 bucks plus shipping and it arrived yesterday. Part of this decision was my fault and I wish I had installed this cylinder sending unit last year - it is far easier and requires no assembly or adjustment. The reason it is somewhat my fault is that during my adjustments, the resistive circuit board lost internal continuity to the connector posts and I took the sender apart to investigate. And whatd'ya know . . . BOING!!! A small internal spring launched itself on a ballistic trajectory for reentry somewhere across the shop never to be found again. Thirty five bucks down the drain but I will be happier to this new style of sending unit.

I have checked the new one for resistance with a multimeter - 0 to 90 ohms - and it works perfectly / accurately. I have also hooked the new one up to the dashboard fuel gauge and this also works perfectly. I did all of this before with the other one before installation into the tank so I suppose there's never a guarantee. But the new sender is installed into the tank and I will put it back into the vehicle very soon.

Rick
 

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Discussion Starter #603
Hello,

My difficulty in Fuel Tank Land never seems to end - my new sender indicates an "open" circuit. It does this in BIT test on the Dakota Digital gauge cluster and when tested using my multimeter. To make matters worse, this occurred during / shortly after getting the assembled tank lifted back into the vehicle.

So I called up Tanks, Inc. and they very generously offered to send me a free replacement which should be here in a few days using the one year warranty clause. The fellow explained that I must have hooked up gauge power to the sender before connecting the gauge ground wire - the power wire had no power on it at connection time. This makes absolutely zero sense to me and he says that this is spelled out in the instructions but I looked at them again . . . no such words about connections are in there. He says this cylinder sender is electronically delicate but since he was so generous about the warranty replacement, I didn't complain.

I will be dropping the tank again in a few days and will be even more methodical and deliberate in checking things this time.

Rick
 

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Discussion Starter #605
Hello Rick,


Its a Tanks, Inc tank made for their company fuel pump and sending unit that's only about a year old. The bolt patterns are made for these devices, no modification required anywhere. Its bolts for both.


Rick
 

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I have their tank, in-tank pump and sending unit in my 65 and it works great. I connected the wires to the sending unit before connecting it to the Dakota control module - with the key off - and it worked immediately.

Because of the geometry of the swing arm sending unit, the gauge in my 83 indicates full for almost 100 miles before it starts to move and then, it drops like a rock. That has always been a problem - to me - and, it's recently gotten worse. I would like to put one of Tanks Inc armless senders in the 83 but, I don't think I could make it fit the stock tank. However, I've been doing some measuring and, I think their FI tank for 68-72 with notched corners could fit the 83. I need to talk to their customer rep to see if I could return the tank if it didn't fit. Also need to save up the $$$ to buy the tank, sender and in-tank pump.

Rick, When you drop your tank to put the new sending unit in, how about measuring how far it is from the left rear corner of the tank to where the fuel filler neck is located. Thanks https://www.tanksinc.com/index.cfm/page/ptype=product/product_id=592/category_id=126/mode=prod/prd592.htm
 

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Discussion Starter #607
Hello Les,


I'm unclear on the geometry of your measurement request. Left rear corner of the tank to where the filler neck enters the tank?


Or . . . left rear corner to the entry of the filler neck / cap location?


Rick
 

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Hello Les,


I'm unclear on the geometry of your measurement request.

Or . . . left rear corner to the entry of the filler neck location? Yes, that.

The dimensions of this tank are almost identical to the measurements of the one in my 83. I'm trying to determine if the filler neck of this tank would line up with the fuel filler door on the 83. If so, - even though Tanks Inc doesn't list it as fitting - it may be adaptable to 5th Gen El Caminos. Until now, 5th Gen owners have been stuck with adapting tanks from early 90s Buick Roadmaster or Chevy Caprice wagons to get a fuel injection tank.


Thanks
 

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Discussion Starter #609
Hello Les,


Its 19 inches from the center of the left rear corner bent tab to the center of the fuel filler neck cap - where the gas goes in. The tank is now mounted but this measurement is a straight, unimpeded measurement with nothing in the way. This, of course, is not the measurement you wanted but was easy to take.


It is 11 inches from the center of the left rear corner bent tab to the entry hole in the body of the fuel tank at the base of the fuel filler pipe. This was also an easy, unimpeded measurement.


The tank and its new cylindrical fuel sending unit is installed and finally working. Though I must say it is more accurate at the low end than the high end. From empty after installing the tank, I poured in five gallons to a twenty gallon tank and the needle went to one quarter - perfect. Then I put in ten gallons hoping to see three quarters on the gauge needle but it went to nearly full - not so good. But OK, I suppose. Far better that its accurate at the low end than the high end.


Now I can use the fuel gauge features in the HDX gauges to hopefully start computing mileage and maybe fuel tank range. We shall see but I'm happy that I finally have a functional fuel tank gauge.



Rick
 

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Thanks Rick
 

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Discussion Starter #611
Hello,

Please don't judge me too harshly with what I'm about to write but yes, I'm probably over-analyzing things below. Maybe I'm even a little nutty.

The LS engine in my EC has some minor-ish difficulty with lean Long Term Fuel Trims (LTFT) according to readings taken with my Bluetooth OBD II modules into various OBD II Android phone apps and Windows PC computer programs. These LTFT numbers indicate that the Powertrain Control Module (PCM) is detecting a lean condition and is adding fuel to all cylinders to richen the mixture back to normal. Here's the nutty kicker for all of you - the vehicle has no OBD II check engine light codes, no difficulty starting, good idle and acceleration . . . really no trouble at all except for spark plug internal porcelain that is a little too white for me. My Check Engine Light (CEL)/ Malfunction Indicator Light (MIL) passes its self tests during engine start so I know it has a good electronic connection to the engine computer. The CEL / MIL light is not illuminated under any conditions except for its self test and no trouble codes of any kind can be read from the engine computer. And without any trouble codes, there's also no PCM freeze frame data.

These OBD II modules also monitor the parameter ID's for both of my oxygen sensors and both sensors appear fully functional. The voltages for each sensor both correctly oscillate back and forth in the proper range to indicate good operation. The PCM is getting this data and is using it correctly.

I've got two of these Bluetooth OBD II plug in modules and I have faith in both of them. One is a $15 EBay purchase and the other is a $50 EBay purchase that reads engine parameters a little faster and also has a good Windows OBD II analysis program. Both of these modules can support Android and I now have four different low cost OBD II analysis programs on my phone - Torque Pro, OBDLink, Car Scanner and MotorData OBD. All four of these Android analysis programs plus the Windows "OBDWiz" program are in basic agreement that the engine is running lean.

Using continuous log-able readouts of the various engine parameter ID's, I can see that the passenger side LTFT is maxed out at 25% extra added fuel at all conditions of idle to 60 miles per hour. The drivers side LTFT is not maxed out at idle but is quite high at around 12-15% but it also maxes out at 25% by 60 mph according to my captured OBD II logs. The Short Term Fuel Trims (STFT) for the drivers side are doing all they can to keep the engine from running lean but the passenger side STFT is beyond the control limits and the LTFT is exceeded all the time.

So I've scoured the Internet and the University of You Tube and it appears that it could be several things. The most common thing with all of these symptoms is a dirty Mass Air Flow sensor (MAF) and I have pictures of it below. I have a K&N air filter and it is quite possible that I have over-oiled it with some of this oil coating the three "hot wires" that are in the center of the MAF. The picture below is my spare MAF that I picked up many months ago and I will clean it up before installing it to see if I can get things back under control.

The idea with the three tiny vertical wires in the MAF is that these wires are electrically heated to a specific temperature and then as the throttle valve opens, the intake airflow cools the wires. The amount of cooling corresponds to the amount of air and this value for air is passed to the PCM to allow for the proper allowance of fuel to the injectors. Ingenious, wouldn't you say?? We shall see tomorrow if my clean spare MAF fixes it. I will also clean up the MAF that is currently installed, if necessary. I will be using a spray can product from the "CRC" company cleverly named "MAF Cleaner" and I'm told this is the only thing that should be sprayed onto a MAF to clean it. WD40 need not apply here and probably not Brake Kleen either. Any of the electronic cleaners that dry with no residue would probably be acceptable.

The other most likely things that could be the problem is an intake manifold vacuum leak or a brake booster vacuum leak and I will also be testing for these things tomorrow. I will use an unlit propane torch flowing propane around the intake manifold to see if it ingests the gas and changes the idle RPM a little. I will also disconnect the vacuum hose from the brake booster hose to see if the vacuum leak goes away and if the LTFT returns to normal.

Given that both sides of the engine suffer from being lean, it is unlikely that all fuel injectors on both sides would behave with spraying too little fuel. However, there is a chance that I could have a fuel pressure problem and I will be installing a temporary pressure gauge at the engine fuel rail tomorrow.

There is also a small chance that an exhaust manifold leak on both sides of the engine could be allowing unmetered air into the exhaust stream that tricks the oxygen sensors into thinking there's too much air. This would tell the computer that the engine is running lean and the PCM would add fuel with higher STFT and LTFT in an attempt to return the fuel mixture to normal. I think the chance of this being the problem is rather low but there is a possibility that my transmission repair people from two months ago did not reinstall my header exhaust manifold gaskets.

We shall see all tomorrow. I may be a little nutty about all of this and may wind up not fixing anything at all. But I have certainly learned a lot about how my PCM operates.

Rick
 

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Discussion Starter #612
Hello,

No large vacuum leaks after extensive searching all around but it is possible I still have a minor leak on the passenger side. I disconnected the brake booster hose and nothing changed so no vacuum leak there either. My exhaust manifold gaskets are also in place.

It looks like it is an over-oiled K&N air filter that is allowing an oil film to be applied to the little wires in the Mass Air Flow sensor - see picture above. With the air cleaner removed and with one of my now sprayed clean MAF sensors in place, the Long Term Fuel Trims (LTFT) on both sides of the engine drop dramatically. The drivers side is very nearly normal in the 0 % to 5 % of added fuel for LTFT as is Short Term Fuel Trim (STFT). Everything on the drivers side is oscillating for fuel control very nicely.

The passenger side LTFT has dropped to about 14% added fuel which is far better than being mostly pegged at a maxed out 25% added fuel. I've removed and installed this over oiled air filter twice and my LTFT numbers have gone up and down twice. Thusly, I at least have a trend of two occurrences and fixes going on here. As I mention above, it is possible that I have small vacuum leaks on the passenger side of the engine that would drive LTFT to still be 14% high but hey, I'm happy that I've at least got these measurements headed in the correct direction. At 14%, they are within the control span of my powertrain control module and fuel injectors and it also does not appear that I need to buy any parts. I priced brand new AC Delco MAF assemblies and they go as high as $279 . . . ouch. A set of new fuel injectors is also expensive.

Now I will go run massive quantities of hot water and detergent through my over-oiled K&N air filter.

Rick
 

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Discussion Starter #613
Hello,


As it turns out, it was a combination of two things that drove my Long Term Fuel Trims high and the oily air filter was only partially to blame. After I washed the air filter last night I had to wait until today for it to dry so that I could do a few long test drives.


Until today, I had the K&N air filter attached with a large plastic elbow and a four inch piece of PVC pipe and it appears that this elbow / extension caused enough turbulence in the air entering the mass air flow sensor (MAF) to disturb the air mass measurement. I can't remember why I felt it was necessary to install the elbow and pipe to mount the air filter but once I mounted the K&N straight onto the MAF, my long term fuel trims fell to nearly zero. The short and long term fuel trims now oscillate plus and minus 5-10% depending on engine speed and vehicle loading. This is how things are supposed to operate and I will check the color of the spark plug porcelain in a few weeks to see if they darken slightly.


I did have to build a small bracket today to support the narrow end of the K&N filter cone. I felt that the not very solid but clamped rubber o-rings and seals were insufficient to carry the weight of the filter mounted to the MAF. Vibration and road bumps could have possibly loosened the filter assembly but its now mounted solidly.


Rick
 

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I was told to have 8" of straight tubing up stream of the M.A.F For proper functioning of the M.A.F.:yell:
 

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Discussion Starter #615
Hello Terry,

It certainly appears that you are correct and I had nowhere near that much straight line tubing prior to the MAF. I had read somewhere that the mesh screen at the front of my MAF sensor was responsible for "straightening" and calming the air prior to its passage over the heated wires. My installed MAF and my spare MAF both still have their screens but it appears that they don't provide much calming to the chaotic air when used with an elbow and a length of PVC pipe.

I took another test drive tonight while logging my LS engine parameters and everything still looks normal for STFT, LTFT and everything else. But now I need to figure out why the excessive values prior to me solving the problem never set a Check Engine Light. Maybe the fellow who programmed my two PCM's turned off more trouble codes than he told me about.

Many thanks,

Rick
 

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Discussion Starter #616
Hello,

I'm beginning to tackle reinstalling the body trim and I can't decide whether to repair / re-polish my original trim or buy all new. Some of these pieces are beyond hope and some are just plain missing. But I think the toughest pieces to replace are my sets of drip edge moldings for a vinyl top but I have all six pieces and they are not so badly damaged. The stainless finish is in good condition on these with only a few small, low dings that I've managed to tap up to being level. I've heard around here the aftermarket repop pieces don't do well on a vinyl topped vehicle.

My stainless piece across the front of the bed below the rear window is the worst. It has been man-handled too many times by others but I've been tapping and raising dents for a few hours with the body hammers. It is going to need the entire 80 grit, 120 grit, 300,400, 800, 1500 and 2000 or more grit sanding process to bring the shine back plus polishing before I will be able to re-install it. And maybe even then it'll be too hideous to look at.

The anodized aluminum door frame trim and lower body trim is badly scratched, dented and the aluminum has oxidized with tarnish. I have started tapping out the low spots with the body hammers and doing a little sanding. I might be able to save the window frame trim because the pieces are smaller compared to the lower body trim. Since a few of the lower body pieces are mangled and missing, I will probably buy the complete set of all new pieces.

You may remember that I bought a complete set of used lower body trim pieces a while back off of Ebay. Indeed, it was a complete set and all were in good condition for only $75. Great deal, I thought, but there was a problem. Turns out, the complete set is apparently for a similar year Monte Carlo which obviously won't do me any good.


Rick
 

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Discussion Starter #617 (Edited)
Hello,

It's oil change day. I'm going to the military base auto hobby shop today and getting the EC up on the lift. I use these days to check for leaks, loose nuts and bolts and to see if anything is rubbing on something else that is not supposed to be rubbed on.

Given that this is a used LS engine with 150,000 miles, I'm not waiting until 3000 miles or more to change the oil and hopefully, these quick oil changes are cleaning the motor internally. The first oil change occurred almost immediately when I had to get rid of the low hanging GMC Sierra truck oil pan that would have scraped on rocks, twigs and insects as my EC trundled down the road. The first oil was the cheapest Walmart oil that money could buy and that only stayed in the crankcase for a few hundred miles and quite a few hours of engine testing parked in the shop.

The second batch of oil went in about a thousand miles ago last July and it was Mobil 1 synthetic. Today, it'll be Shell Rotella T6 synthetic because I have learned that it has a better oil additive package that fights wear. A NAPA Gold oil filter will also go in.

I had to call OPGI yesterday about my order of body, door window frame and tail gate trim. I had no choice but to order the body and tail gate trim because so many pieces were either mangled or missing. I have the door window frame pieces and I worked on them last weekend but it was going to be a lot of work to make them usable again. But they still have not shipped my order after submitting it last Monday. I knew the body trim was going to be back ordered for 4-6 weeks but the other items are in stock. Cyber Monday musta' crushed them for parts orders.

When I bought my oil and oil filter recently, I noticed that I was missing a Rally wheel cap. Fear not, this isn't an original. Its an inexpensive, plastic, ten buck replica from Jegs that got here Thursday and went on that night.

Rick
 

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Discussion Starter #618
Hello,

I did something mechanically significant today with the LS engine and I had no idea that it would be such a boost - I took about an inch of slack out of the throttle cable.

This cable is a standard length throttle cable for a 5.3 liter motor out of a 99 GMC Sierra truck and I have had it hooked up to my original 1970 throttle pedal. But I've always known that the pedal never felt very good or very high up off the carpet on the floor. With the 2.73 gears in the differential, a fully mashed accelerator pedal buried into the carpet would cruise all day long at over 80 miles per hour. Not bad and plenty fast enough for a nearly fifty year old vehicle but it certainly never reached that speed very quickly. Until now.

Yesterday, I wedged the throttle pedal to the floor with a long tube - engine off - here in the shop and went forward to see how far the throttle blade was open. It was only open about 1/3rd so it finally was confirmed that I needed to do something. Using a cutoff wheel, I removed the swaged cable stop from the end of the throttle cable closest to the pedal and then slid a new aluminum crush-able end over the cut end and then crimped it with vise grip pliers . . . removing about an inch of cable slack.

The pedal was then well above the carpet and at the height that I remembered most GM accelerator pedals to be at in the 70's. It felt good so I started the engine and checked the idle. It settled into its normal 800 RPM which meant that I had not removed too much slack. Then I headed out for a test drive to see things in action. Backing out of the shop and onto dry grass to get turned around, I immediately knew that this was going to be fun - I spun a rear tire on my EC for the very first time. It was not a lot of wheel spin but it did startle me a little with the accelerator pedal and throttle blade in new territory for me.

So I headed down the road and I finally have the engine operating as it should. The acceleration is much more brisk but with those 2.73 gears, a tire fire spinning with smoke will still be difficult and I'm not much for abusing the equipment anyway. Accelerating away from a stop with the throttle buried a little deeper, I can now detect sweeter engine sounds through that K&N air filter that I never had before. I need to check if the throttle body has reached fully wide open with this but I'm thinking its probably reached 80-90% fully depressed. No matter, this was still a very rewarding repair . . . upgrade????

I have also quieted down the buzzy rattling of the sheet metal hatch over the smuggler's area. Using short lengths of thick, adhesive-backed rubber, I spaced 10-12 pieces around the perimeter of the hole. Now its all quiet. No sheet metal banging, clanging or buzzy-ness every time I hit a bump in the road.

Today's 15 mile test drive was good. I got rid of one collection of bad sounds and gained some good engine noises and acceleration.

Rick
 
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