90 zr1 no start

[scottfab]

Originally Posted by mfranklin162

I have 47-48 psi that hold well, when innitially crankling I get 1 injector pulse and it may pulse once in a blue moon while cranking.

Starting to sound more like the crank position sensor like Jerry said.
Consult the FSM for details.

[VetteVet]

No or intermittent crank position sensor signal = no or reduced ref pulses from ICM to ECM and tach. Easiest way to check is to see what your tach is doing while cranking. If tach is showing cranking RPM, then crank position sensor and ICM are doing their part to provide ref pulses to ECM which are used for injector triggering.

Jep

[XfireZ51]

Jep,

That's what I was thinking. The intermittent injector pulse is coming from the cam sensor indicating #1. But the injectors won't pulse unless the ECM is seeing
DRPs, No DRPs w/o crank sensor.

[Hib Halverson]

The same OP was on the CAC.

Since you've already replaced the ECM and the DIS module (very expensive so far, I'd think), your problem may lie in either the wiring and connections between the engine and the ECM, between the engine and the DIS module, with the injector wiring or with the fuel supply. system.

Also, in the rare case where the SIR's DERM is disconnected, the engine won't start. If you find it discon. Reconnect it and try starting.

First, stop trying to run the engine on carb cleaner. Spray carb cleaners are very low octane and may damage the engine.

Also, you said you have spark but didn't say how you tested for it. When you test spark, be careful how you do it. One wire at a time with all the other wires connected. If you do it other ways, you may damage the DIS module.

Next, you need the Factory Service Manual and you should start with Chart A3 "engine cranks but won't run" on page 6E3-A-21. If you don't have the FSM, you need to get one and '90 is the only year during the LT5's run where the book is two volumes. There is the big book then a "Section 8A Supplement" and you need both. CAC sponsor, Zip Products, usually has them in stock.

The "cranks but won't run" diagnostic is 4 pages and requires some time to do, but if you run that diagnostic you'll likely find the problem.

To run the cranks but won't run diagnostic, you need a scan tester, a 12v test light, a spark tester, an injector test light (or "noid light) and your fuel pressure gauge.

Run the first part on Chart A3 pg 1 and post the results.

[ghlkal]

OP, here's the first page in the FSM

If you don't have this, I can post the other pages - LMK

[Schrade]

Originally Posted by Hib Halverson

The same OP was on the CAC.

Since you've already replaced the ECM and the DIS module (very expensive so far, I'd think), your problem may lie in either the wiring and connections between the engine and the ECM, between the engine and the DIS module, with the injector wiring or with the fuel supply. system.

Also, in the rare case where the SIR's DERM is disconnected, the engine won't start. If you find it discon. Reconnect it and try starting.

First, stop trying to run the engine on carb cleaner. Spray carb cleaners are very low octane and may damage the engine.

Also, you said you have spark but didn't say how you tested for it. When you test spark, be careful how you do it. One wire at a time with all the other wires connected. If you do it other ways, you may damage the DIS module.

Next, you need the Factory Service Manual and you should start with Chart A3 "engine cranks but won't run" on page 6E3-A-21. If you don't have the FSM, you need to get one and '90 is the only year during the LT5's run where the book is two volumes. There is the big book then a "Section 8A Supplement" and you need both. CAC sponsor, Zip Products, usually has them in stock.

The "cranks but won't run" diagnostic is 4 pages and requires some time to do, but if you run that diagnostic you'll likely find the problem.

To run the cranks but won't run diagnostic, you need a scan tester, a 12v test light, a spark tester, an injector test light (or "noid light) and your fuel pressure gauge.

Run the first part on Chart A3 pg 1 and post the results.

OP; did you replace these parts? Why? What test confirmed broken parts?

If you're replacing parts without testing, I have the solution, 100% guaranteed:

DTC 0001vette. Replace vette. Send me old 'vette' and a small check for disposal fee of good 'part' [vette], and I guarantee at least equal success (or better) with replacement part [car].

[mfranklin162]

Ran flow chart a-3 by the book!! That is why I replaced the module, all pins tested good end to end!! Also ran crank no start chart, it stated to replace ecm, I happen to be an ase certified gm technician, I do not hang parts!!!! I went with the test results from the manual!! Hears a good one for ya, let car sit all last week, pushed it back in shop battery was low from sittin in the cold, charged battery while I was doin other things. When I went to the car hit the key and started right up.

[Dynomite]

Originally Posted by mfranklin162

Hears a good one for ya, let car sit all last week, pushed it back in shop battery was low from sittin in the cold, charged battery while I was doin other things. When I went to the car hit the key and started right up.

I am thinking if you topped off the battery to start with
Sounds to me like a tad more voltage solved the poor connection including a poor ground (wherever it was) issue

[scottfab]

Realistically it sounds like an intermittent and likely to come back.
It's best that it does now so you can find it.
No one likes to break down unexpectedly.
Keeping good notes on what you've done in what order
could be very valuable later on.
You'll need a game plan if/when it comes back.

Intermittent problems are the worst.

[mfranklin162]

Well, it started and ran two times, no wont start again, have not had time to get back on it, been pretty busy! Will post what I find when I find it!!