2000 Chevy 7.4 no-start

[mk378]

Hello all. My friend has a 2000 model year Chevy K3500 truck with the 7.4 liter gas engine and automatic transmission.

He started it up normally from cold and drove about 200 feet to where it stalled and would not re-start. It cranks but does not start.

I have checked the following:
Gas tank 1/4 full. He even added some gas to be sure.
He replaced the battery (needlessly of course) before I got there. That was the battery on the right side of the truck. By the way, what does the extra battery on the left side do?
Sparks at 2 of the wires (only 2 tested)
Fuel pressure 59 psi key on, fluctuates around 57 while cranking, drops to 55 key off and holds there for at least a couple of minutes.
No fuses blown either in the underhood box and the one by the driver's door (are there more fuses?)
Code scanner connects to PCM normally and reports no codes are stored. I cranked for about 20 seconds constant to try and retrigger any codes that might have been erased when the battery was removed.

Live data from code scanner reports seemingly sane readings from all the major sensors:
Engine rpm: 0 when not cranking, 190 while cranking. (I assume this is from the CKP?)
IAT and ECT: about 60 degrees F, which is ambient here.
MAP: 28 inHg not cranking 27 while cranking.
MAF: 0.3 lb/min not cranking about 1.0 cranking.
TPS: 0 to 100 smoothly varies with throttle position.

So this fine American machine should start right up, right?

 

[spasm3]

Check compression to see if there is a timing chain issue. How many miles on it?

 

[mk378]

137,000 miles. Everything under the hood is almost certainly original.

I thought there was a "cam out of sync" code but you're right, any non-running engine deserves a compression check.

 

[spasm3]

Originally Posted By: mk378
137,000 miles. Everything under the hood is almost certainly original.

I thought there was a "cam out of sync" code but you're right, any non-running engine deserves a compression check.


At 137,000 it should not have jumped a timing chain tooth , unless its really been neglected. If you have a noid light , check the injectors while cranking as well. Does this engine have a crank position sensor?

 

[Ojustracing]

You have fuel pressure. But are you getting fuel out of the injectors? can you at least smell fuel after cranking trying to start???

 

[mk378]

It didn't look like there is a way to reach the injectors without taking the big aluminum top of the intake manifold off. Maybe there is a way to sneak in and unplug one.

Yes what I saw on-line about it there is a crank position sensor, cam position sensor, but unusually a single coil and a distributor for the 8 plugs.

 

[jasonal]

change the fuel filter, probably plugged partially. think you need 62 psi before injectors will open.

 

[Number_35]

Sounds like you've checked all the basics ... you need compression, the correct air-fuel mixture (i.e. roughly 14:1), and a spark at the right time. If it's got those, it should run!

Please let us know what it turns out to be.

 

[Ramblejam]

Originally Posted By: mk378
So this fine American machine should start right up, right?


Sure, but you'll first need to fix the distributor.

 

[Trav]

Spray a little ether, if it fires you know the injectors are not firing. Diagnosing is pretty basic from there.

 

[mk378]

Thanks for the suggestions. I called him and had him check for gas smell at the tail pipe-- no. Then he tried ether-- nothing, not even backfiring.

So Ramblejam, are you talking about rotor burn through? There really isn't much inside that distributor but I guess I need to fight my way back there and get the cap off. I did see sparks on my test plug but maybe they aren't strong enough. I could also check at least coarsely for cam sync that way.

This truck is in a field, it has been raining all week, and his sister's "dogs", which are more than 1/2 wolf, may appear on the scene at any time. I'm a cat person... so I get a little distracted about running the basics out there.

So maybe he'll just have the dealer tow it in and deal with it. He does know some people in the service department so it wouldn't be too bad. It's really burning at me to not be able to fix it though.

 

[another Todd]

I didn't know the 7.4 was still around in 2000.

Last GM no start I played with had a badly corroded distributor cap and rotor with lots of evidence of arcing. Just changed those two items, it started right up, and the owner drove it and said it ran better than it had in years. Even with the bad cap and rotor it would still throw a spark with a screwdriver in the boot held over a ground, but not enough juice to fire the plugs.

 

[wtd]

I have a 98 Chevy 1 ton truck with the 7.4L and these engines along with the 5.0 and 5.7L can have distributor problems. When I first bought this truck, I had to zip tie the cap to the distributor because both of the plastic screw ears on the distributor were broke out. I bought a metal bodied distributor off of Ebay and it has been fine ever since.

I also had the cap and rotor in the 5.7L in my other 98 chevy truck corrode to the point that the truck would hardly run.

I also had a vehicle years ago lose the metal point on the rotor so that the vehicle died and wouldn't run

 

[rationull]

That sounds almost EXACTLY like an experience I had with a 1999 Suburban 7.4 a couple years ago! Pulled out of the driveway and about 100-200 feet on the road and the truck died. Would crank but not start, etc. There was spark, but when checking the spark with a timing light I noticed that the spark timing was uneven between cylinders.

I ended up changing the distributor cap and rotor, as well as the cam position sensor which is on the distributor.

My fuel pressure appeared a bit low when testing but that was NOT the problem. The cap and rotor also looked fine in my case, and I had had them off for an unrelated repair and opted not to replace them a few months prior to this problem which was frustrating

My repair was chronicled here: http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2907434

Good luck and do report back!

 

[mk378]

May have a break in the weather today. Going to try to get over there armed with a new cap and rotor and try it. Thanks for the advice.

 

[rationull]

I don't remember exactly how the rotor comes off but be sure to keep the distributor aligned correctly if you have to remove it for whatever reason. It's kind of a bear to adjust with everything installed.

 

[mk378]

Update: Problem is solved.

Summary: It was the wire from the coil to the distributor.

I dug down there and got the cap off, and found it was an aftermarket one in rather good condition. As was the rotor. The cap had a date marked on it that it was made in 2013. Friend did finally remember that the cap, rotor, plugs, and wires were replaced about 2 years ago.

Decided not to spend $60 on a "parts changing" excursion and re-assembled with the old parts. Then, "so we won't look like idiots", insisted on trying to start once more before having it towed away.

And it started... or acted like it would. Lots of backfiring like the firing order was wrong. Because it was... I had ASSUMED that since the wires are lined up in two groups of 4 on the cap, they just connect to the cylinders in that order. They do not, though there are tiny numbers on the cap to guide you. In other words, the 4 wires on each side of the cap do go to the 4 plugs on that side of the engine, but not in order.

Straightening that out, the engine started and ran, but I could hear stray sparks popping somewhere near the back. Saw it was from the coil wire to the very nearby harness bracket. There was a cut/burn/hole in the wire insulation. I guess it was closer to the bracket initially, and shorting out the sparks more completely, so it wouldn't run at all before.

Bought a new wire and all is good, or at least mediocre like all his other machines are. It does roar to life at the turn of the key, but starts to sputter a bit a few seconds later when it comes off fast idle. "Oh yeah, it always does that..." CEL came on almost immediately after starting so there are some clues there. But that is for another day.

 

[ls1mike]

Nice! Easy Peasy. I had something similar happend to my 6.0 Chevy.
I am pretty anal about maintenance and I changed the plug wires with ones that should not have required the factory heat sheilds or so I thought. Should have put them on for towing. Long story short it got hotter than 500 degrees near the exhaust manifold and it melted the plugs wires on the bottome side so you couldn't see it. Truck had a miss, I assumed the CPS was going bad, when I craweled under it I saw that the new wires were bad.

 

[KenO]

Probably needs a distributor (distributor houses the cam sensor). They're plastic and the bushings fail rocking it out of alignment. I've had good luck with the $50 billet ebay one. Check for codes, if it has a cam out of sync, then I'd be looking at cam and crank sensor first.

 

[rationull]

Nice! Glad you got it fixed and sounds like you got out easy (aside from the PITA that is taking the distributor cap off on that engine setup)!