1998 LC Crank but no start (not immobilizer) (1 Viewer)

[richg]

My '98 LC (~367K on it) just started this issue. It will intermittently have a tough time starting, happens about 50% of the time now. It cranks fine and fast, but will not fire up. It does not matter if cold or hot, if I just stopped the engine and tried to re-start, or if truck has been sitting overnight. Sometimes I will let it crank for like 7-8 seconds and no go and then stop, turn the key again and it fires right up. Once running, it runs mint with no issues.

I do not believe this to be an issue with the immobilizer as when I insert the key the CEL is on and the immobilizer security light turns off (and stays off during cranking). In addition, I made a jumper from contact F in the EFI relay spot to the battery and the issue is still present.

EFI fuse looks fine, not hot at all. I put in a 30A one just in case but that hasn't changed anything either.

I have not yet tested for spark/fuel yet, but figured I'd ask for other potential things to check in the meantime. I'm thinking it is fuel as I don't see/smell a big puff of unburnt fuel out the exhaust when it finally fires up.

I am guessing that there is some other bad connection within the fuse box that is causing this...

 

[Trunk Monkey]

At that mileage I'd start with the fuel pump.

 

[NookShneer]

I was running into the same issues with mine. I ended up swapping in a rebuilt starter and it has solved the starting problems.

 

[medtro]

Check fuel pressure and crank sensor.

 

[richg]

I hooked up a fuel pressure gauge and left it in the garage for a couple weeks starting it from time to time. Could not get the issue to replicate! Only thing I noticed was sometimes the fuel pressure bled down pretty quickly after shutdown (eg, ~1min to get back to 0), other times, it had a very slow decay and would still be sitting at 20+ psi overnight). I'm back to driving it and the issue has only happened one time since.

I don't have a way to test the crank sensor (is this something I can do if I get techstream or do I need a oscope?), but highly doubt that is the issue since the truck has never had an issue once running. It is only at startup.

What can I use to verify if injectors are actually firing? The noid lights I have (similar to this) are all 3 ohms, vs our injectors at ~12. I could wire a resistor in series...

I am thinking it is fuel pump, perhaps check valve going/gone bad and fuel drainback based on way the truck is parked?

 

[silvarshooter]

Fuel pumps are cheap and about an hour job including clearing for access, might as well knock that out and go from there.

 

[Kamran Khan]

To test a faulty cam position sensor or crank position aka engine speed sensor, get a multimeter unplug those two cam position sensors and 1 crank position sensor, set the millimeter to ohms, each sensor should have resistance between 950-1250 ohms. If the resistance is higher or lower than the specified value that will indicate faulty sensor. The resistance value that I am writing here is from 1UZFE engine and I believe 2UZFE may have similar value

 

[2001LC]

I hooked up a fuel pressure gauge and left it in the garage for a couple weeks starting it from time to time. Could not get the issue to replicate! Only thing I noticed was sometimes the fuel pressure bled down pretty quickly after shutdown (eg, ~1min to get back to 0), other times, it had a very slow decay and would still be sitting at 20+ psi overnight). I'm back to driving it and the issue has only happened one time since.

I don't have a way to test the crank sensor (is this something I can do if I get techstream or do I need a oscope?), but highly doubt that is the issue since the truck has never had an issue once running. It is only at startup.

What can I use to verify if injectors are actually firing? The noid lights I have (similar to this) are all 3 ohms, vs our injectors at ~12. I could wire a resistor in series...

I am thinking it is fuel pump, perhaps check valve going/gone bad and fuel drainback based on way the truck is parked?

98-05 fuel pump failure. Is often proceeded with long cranks and or no start cranks, but start normal at times. At some point, it fails completely.

Watch fuel pressure each time you crank, may be revealing. If low or no pressure, bad fuel pump (9 out of 10 times) and or clogged fuel filter and or sock (in tank). This assume you've good fuse box (immobilize), and fuel shut off (accident safety device) working properly.

Dropping to 0 PSI fuel pressure in one minute, is a failed leak down test. Stating result of all 3 test FSM prescribes, helps!
1) Engine off, run fuel pump with tech stream. spec - 38-44PSI
2) Engine idling. Spec 38-44PSI
3) Once engine shut down. Pressure should remain 21 PSI or more, for 5 minutes. (leak down test).

At your age and miles. I'd do all 3 fuel pressure & leak DN testing above. Any failures: I'd likely just go ahead and replacing fuel pump w/sock (if sock looks bad), fuel tanks top O-ring seal and fuel filter. I'd re-run tests, and if any failures. I'd then replace FPR (fuel pressure regulator). If still failing leak down, I'd pull fuel injectors and send out to be tested, cleaned and rebuilt. Replacing any bad ones.

Also make sure to scan for DTC pending. Crank or Cam sensors intermittent short, "may" not become confirmed setting off CEL. But may show-up as pending. Provided, you check before key turned off. You may also see lean DTC pending, which would likely be fuel starvation (bad fuel pump).

 

[Travis Bickle]

When it doesn't start does your check engine light illuminate with the key on? If not it's probably the old fuse box issue.

I would not just start shotgunning parts.

 

[76lcmike]

When it doesn't start does your check engine light illuminate with the key on? If not it's probably the old fuse box issue.

I would not just start shotgunning parts.

My '98 LC (~367K on it) just started this issue. It will intermittently have a tough time starting, happens about 50% of the time now. It cranks fine and fast, but will not fire up. It does not matter if cold or hot, if I just stopped the engine and tried to re-start, or if truck has been sitting overnight. Sometimes I will let it crank for like 7-8 seconds and no go and then stop, turn the key again and it fires right up. Once running, it runs mint with no issues.

I do not believe this to be an issue with the immobilizer as when I insert the key the CEL is on and the immobilizer security light turns off (and stays off during cranking). In addition, I made a jumper from contact F in the EFI relay spot to the battery and the issue is still present.

EFI fuse looks fine, not hot at all. I put in a 30A one just in case but that hasn't changed anything either.

I have not yet tested for spark/fuel yet, but figured I'd ask for other potential things to check in the meantime. I'm thinking it is fuel as I don't see/smell a big puff of unburnt fuel out the exhaust when it finally fires up.

I am guessing that there is some other bad connection within the fuse box that is causing this...

check the connector on the drivers side underneath near the frame rail even with the rear driver's door. it's part of supply voltage circuit to the fuel pump. it maybe corroded.

 

[richg]

Dropping to 0 PSI fuel pressure in one minute, is a failed leak down test. Stating result of all 3 test FSM prescribes, helps!
1) Engine off, run fuel pump with tech stream. spec - 38-44PSI
2) Engine idling. Spec 38-44PSI
3) Once engine shut down. Pressure should remain 21 PSI or more, for 5 minutes. (leak down test).

I left it in my garage for a couple weeks starting it multiple times a day with fuel pressure gauge hooked up. Issue never replicated unfortunately. Fuel pressure is nominal when running. I don't have techstream so haven't tried to turn the pump on with engine off. Sometimes, fuel pressure dropped down rapidly after a shutdown, but I'm not sure if that was a result of a leaking bleeddown valve on my fp gauge setup vs. something in the system. Because other times, it held over 21 psi for over 12 hrs. Either way, whether pressure bled down or held, FP rose rapidly when cranking and truck started up -- but again, the issue didn't replicate for me unfortunately while I was testing.

I really do believe it to be fuel related as when it does start up (after experiencing the issue), there is no big puff of black/grey rich exhaust when it fires.

What can I use to verify if injectors are actually firing? The noid lights I have (similar to this) are all 3 ohms, vs our injectors at ~12. I could wire a resistor in series...

check the connector on the drivers side underneath near the frame rail even with the rear driver's door. it's part of supply voltage circuit to the fuel pump. it maybe corroded.

I'll check this out, thx. I could see something like this being the issue. I did end up ordering a fuel pump and filter so will hopefully get that swapped and check this out this weekend.

What I'm finding now when driving it, is that if it doesn't start after the normal 2-3 seconds of cranking. I just stop cranking, then immediately turn the key to crank again and it fires right up.