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Old 01-03-2017, 11:54 AM
toyinhawaii toyinhawaii is offline
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Default Help for trouble shooting for a "no start"

Trying to trouble shoot my no start.
This is a project and thought I was all ready to start it up and all I got was it just cranking over. Heres a little history.

1) LT1 has been rebuilt with the only mods done are .30 over pistons and camshaft

2)I am getting fuel into the injectors, all injectors are getting power(about 12.?? volts) but the plugs are dry..seems like the injectors aren't opening. The last time the engine ran was about 9-10 yrs ago. I'm sure that there was a small amount of fuel in the injectors but when it came time to put them back in,all I was able to do was shoot some carb cleaner into the top area and where the nozzles were (this was done about a year ago). Hope their not seized up.

3) I am getting spark into the plugs. Therefore I'm pretty sure that the PCM is getting power to run everything else.

4) I am concerned about the oil pressure. Even though I can crank it, I don't get oil coming up into the heads nor does it go up into line from the rear of the intake were I have my mechanical oil pressure gauge hooked up. I have only cranked it over for about 5-10 seconds at a time,about 3-4 times. Was this long enough for the pump to eventually start pumping oil? I was thinking about manually priming the pump by taking off the fittings for the oil pressure and sticking a flat head screwdriver styled rod down it attached to a drill. Is this the right way?

5) As far as it getting air. I guess the MAF is working to regulate the flow.. as long as the PCM is getting power going to it that's all I can assume.

Thanks in advance for the help
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  #2  
Old 01-03-2017, 12:01 PM
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Was VATS programmed out of the ECM? That will keep the injectors from firing, even though everything else is working. You may be able to rent a NOID kit at your local auto parts store, to test the injectors actually firing. If they are firing, but no fuel, and you have pressure at the rail, then back to more troubleshooting.
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Old 01-03-2017, 12:16 PM
toyinhawaii toyinhawaii is offline
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Quote:
Originally Posted by darbysan View Post
Was VATS programmed out of the ECM? That will keep the injectors from firing, even though everything else is working. You may be able to rent a NOID kit at your local auto parts store, to test the injectors actually firing. If they are firing, but no fuel, and you have pressure at the rail, then back to more troubleshooting.
Yes, when I initially swapped the LT1 in about 10 yrs ago I drove it in the elky for about 2 weeks before I started my project and the PCM was reflashed.
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Old 01-03-2017, 12:35 PM
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injectors may be stuck??
they get 12v all the time, the ecm triggers the ground..

is the oil filter full of oil??
you may not have cranked it long enuff ether
sometimes it takes about 30-40sec in a row of cranking for my hotrod to show pressure..

no you cant prime the oil pump on a lt1 without removing the intake and pump drive stub/gear..

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Old 01-03-2017, 12:38 PM
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OK, so VATS should not be the issue. I would then get the NOID lights and see if the injectors are firing. You can also measure the resistance of the injectors to be sure they are not open ( 14-16 ohms nominally) ( wouldn't expect all of them to be open, nor would I expect all of them to be plugged up either). Injectors fire via a ground signal from the ECM. Would have 12V all the time- just waiting for the ground signal to fire. If you have 2 fuses for injectors, make sure both are good.

How's your fuel pressure? Assume pump primes for 2 seconds, then cuts off. regulator holding pressure for at least a couple of minutes after pump shuts off? Pump should re-start when Oil Pressure builds, or revs show engine is running. A lot depends on how the relay was wired- could have been wired direct with no Oil Pressure switch. Will engine run using starter fluid squirted in the TB?

Engine should start whether MAF is plugged in or not. If not plugged in or defective, ECM will use a default table. IAC is involved more with starting, but again should not inhibit it totally.

Not sure how to prime an LT1- hopefully JJ jumps in
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Old 01-03-2017, 01:12 PM
toyinhawaii toyinhawaii is offline
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Quote:
Originally Posted by JJLT1 View Post
injectors may be stuck??
they get 12v all the time, the ecm triggers the ground..

is the oil filter full of oil??
you may not have cranked it long enuff ether
sometimes it takes about 30-40sec in a row of cranking for my hotrod to show pressure..

no you cant prime the oil pump on a lt1 without removing the intake and pump drive stub/gear..

injectors may be stuck??....it would seem strange that their all stuck, but not under the circumstance that its been sitting all these years....is just lightly tapping the sides the remedy to free them up?


they get 12v all the time, the ecm triggers the ground.....how would I know if the ECM does trigger the ground..is there something I can checked?

is the oil filter full of oil??.....MMMM idk...I would think maybe not, considering I cant get oil up into the heads...but that reminds me of when the first time I tried to crank it over (10 yrs ago) and it wouldn't start...couldn't figure it out and then I connected the 2 brown wires going into the side of the oil pan for the ...I believe its the "low oil level sending unit"...those 2 wires were jus dangling there so I connected them and she started right up...took me a week to figure that one out...
this was the first time I started to realized that "going from old school carburetor to new school fuel injection was what put the fear into some people.

you may not have cranked it long enuff ether....ok , I didn't want to crank it too much considering that all I have in the cylinders and heads is engine lube.


no you cant prime the oil pump on a lt1 without removing the intake and pump drive stub/gear.....ahhhh...ok, I was trying to make sure that the oil pump was turning so when I pulled the valve cover I saw my rockers going up and down so I assume since the pump is meshing with the cam that its working too, that was the only thing I could think of to do.
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Old 01-03-2017, 01:54 PM
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You say you're getting fuel to the injectors, but is the pump on and making pressure? You mention oil pressure, so that's why I'm asking. LT1's have a 'failsafe' in factory installs such that no oil pressure at the sensor means no fuel pump run. Bad sensor or no oil pressure prevents it. Just a thought.
Patrick
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Old 01-03-2017, 01:58 PM
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Quote:
Originally Posted by darbysan View Post
OK, so VATS should not be the issue. I would then get the NOID lights and see if the injectors are firing. You can also measure the resistance of the injectors to be sure they are not open ( 14-16 ohms nominally) ( wouldn't expect all of them to be open, nor would I expect all of them to be plugged up either). Injectors fire via a ground signal from the ECM. Would have 12V all the time- just waiting for the ground signal to fire. If you have 2 fuses for injectors, make sure both are good.

How's your fuel pressure? Assume pump primes for 2 seconds, then cuts off. regulator holding pressure for at least a couple of minutes after pump shuts off? Pump should re-start when Oil Pressure builds, or revs show engine is running. A lot depends on how the relay was wired- could have been wired direct with no Oil Pressure switch. Will engine run using starter fluid squirted in the TB?

Engine should start whether MAF is plugged in or not. If not plugged in or defective, ECM will use a default table. IAC is involved more with starting, but again should not inhibit it totally.

Not sure how to prime an LT1- hopefully JJ jumps in
Darbysan...I was replying to JJ before i saw your post....

I would then get the NOID lights and see if the injectors are firing. You can also measure the resistance of the injectors to be sure they are not open ( 14-16 ohms nominally) ( wouldn't expect all of them to be open, nor would I expect all of them to be plugged up either). Injectors fire via a ground signal from the ECM. Would have 12V all the time- just waiting for the ground signal to fire. If you have 2 fuses for injectors, make sure both are good.......oh,..ok..I was looking in my service manual about the testing of the injectors but wasn't quite sure what that tester was that it was showing nor to savy on how to interpret it i guess its what your referring to as the "NOID lights ".. I"ll try that OHMs test and double check the fuses like you said.


How's your fuel pressure? .......pump is pumping but my pressure gauge on the Schrader valve doesn't read any PSI...suppose to be 43.5 psi ,, right?
Assume pump primes for 2 seconds, then cuts off......actually,before I had an MSD fuel pump hooked up with a 30amp relay then to the 15 amp fuse..it worked. Now I went back to the OEM pump in the tank, I noticed that after the key was on,and it pumped fuel, the fuel did shut off... I didn't understand why so I went back to hooking my in tank pump straight to a 30 amp relay then to the 15 amp fuse...it runs constantly now. This is a brand new Delphi, that puts out 65-90 psi.

regulator holding pressure for at least a couple of minutes after pump shuts off?........mmm not sure but this is also a brand new Delphi regulator


Pump should re-start when Oil Pressure builds, or revs show engine is running. A lot depends on how the relay was wired- could have been wired direct with no Oil Pressure switch.......... I wired it 2 ways...1 way with the oil pressure switch hooked up and now with it direct (w/ the mechanical oil gage)

Will engine run using starter fluid squirted in the TB?....didn't try that considering I stopped when I saw I had no fuel going into the cylinders.

Engine should start whether MAF is plugged in or not. If not plugged in or defective, ECM will use a default table. IAC is involved more with starting, but again should not inhibit it totally. .........ok, thanks
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Old 01-03-2017, 02:06 PM
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x2 on the NOID light to see if the ecm is trying to fire the injectors..

x2 on the startin fluid, running it some may free up some stuck injectors,
yes they do stick, they can stick open/leak too..
now days fuel gets real funky in 9-10yrs.. some fresh gas in there may help??

if you changed the filter? if you did not fill the filter with oil? it will take a lot of cranking to fill it..
you can backfill the oil gallys from the oil pressure port..

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Old 01-03-2017, 02:07 PM
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Spray some starting fluid in it. If it starts you have a fuel delivery problem.
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Old 01-03-2017, 02:11 PM
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the fuel pump does not have to have oil pressure, unless you wired it that way..
distributor pulse will trigger the fuel pump too..

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Old 01-03-2017, 02:16 PM
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Quote:
Originally Posted by pbr400 View Post
You say you're getting fuel to the injectors, but is the pump on and making pressure? You mention oil pressure, so that's why I'm asking. LT1's have a 'failsafe' in factory installs such that no oil pressure at the sensor means no fuel pump run. Bad sensor or no oil pressure prevents it. Just a thought.
Patrick
hi Patrick,
yes, I am getting fuel to the injectors...not sure about that pressure...cant see any PSI on my pressure gage I have hooked up to the Schrader valve.

I took off the OEM pressure sensor...(are we talking about the one at the rear of the intake?) and installed a mechanical gage...its been some time since I did the original swap out from the caprice but I recall it maybe only had a warning light...that's why I went with a mechanical,c ause I wanted to see the oil pressure...if I recall the 3 wires coming out of the pressure switch...they were, Orange for 12v, gray was tied into the fuel pump orange for 12v in case the fuel pump lost 12v juice and the tan was for the gage/idiot light...but like I said..i think it was the idiot light.

could it be that it does have to have an oil pressure switch hooked up? cause I went on autozone..just looking at the oil pressure sensors and it listed 2....1 sensor if equipped with warning light and 1 sensor if equipped with gauge.....if so than that means I can not go with a mechanical gage..i would have to go with an electric one??
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Old 01-03-2017, 02:25 PM
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Quote:
I went back to hooking my in tank pump straight to a 30 amp relay then to the 15 amp fuse...
it runs constantly now.
must not need oil pressure..

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Old 01-03-2017, 02:40 PM
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With the Fuel Pump running, you should be seeing 40-50 PSI of pressure at the fuel rail. If not, need to check from there back to the tank- May be a plugged filter, or split connection hose in the tank. The hose in the tank that connects the pump to the sender needs to be a "special" grade of fuel hose (SAE 30R10), designed for being submerged in gas. Normal Fuel Injection hose will disintegrate over time when submerged. I've even seen the special stuff be bad out of the box, especially when it is supplied as part of a kit. Maybe just shelf life on the kit stuff.
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Old 01-03-2017, 02:49 PM
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is the fuel regulator adjustable??
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