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'94 Camaro 3.4L Cranks but No Start

44912 Views 45 Replies 7 Participants Last post by  Spoonyg
Hello, I bought my Camaro new in 1994 and have had very good luck with it until this past Sunday. My son backed it out of the driveway and when he put it in drive, it quit running and I haven't been able to start it since. The first thing I did was to check the oil and it smelled strongly of gasoline. The engine turns over, and sounds like it wants to start but won't.

I have replaced the following items with new parts: Spark plugs, SP cables, Ign. coils (all 3), O2 sensors (the 2 on the exh. manifolds), air filter, fuel filter, and fuel pump. I have also changed the oil and the oil filter.

I'm kind of stuck now on how to proceed, (my limited imagination is at an end at the moment) whats the next step, shy of towing it to a real mechanic. Any and all suggestions will be greatly appreciated.

Thanks Brad
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I got it all back together last night. Believe it or not, I'm really having fun with this. However, it would really be frustrating if this was my primary car.

I'll (hopefully) refill the oil and anti-freeze this afternoon and will post back with the results. I'll check the ECM resistance while filling the oil.

The SES not flashing is really bugging me. I checked online and found new ECM's for around $100 (not-programmed). What am I looking at for programming. I haven't checked online or locally yet. If I remove the ECM, can I take it somewhere locally and have a diag ran? Also, the battery is disconnected right now so the ECM should reset when I hook the battery back up. I've checked every fuse, that I know of, and none are blown.

What is the best way to check the TPS voltage without destroying the integrity of the wires (I'm thinking some sewing pins).

I plan to re-read this whole post this afternoon also to see if I missed anything you folks have said.

Thanks again, I'll post back in a few hours and let you know about the outcome.
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The connector for the TPS can be back probed if you use paper clips to extend the probes. Just remember, what ever route you take to measure, don't let the two leads touch each other. Check the attachment of the TPS sensor, if there are slotted holes, then its adjustable, loosen the screws and rotate. If it is not, you may have to bend the tab. The ECM will tell you if the TPS voltage is set too high or low.

ECM in the diagnostic mode should flash out code 12, if it is an OBD I.

The ECM without the prom is called a controller, the protector for the prom. On later models, starting with 1990(?), the prom is soldered into place. One has to remove the cover and see, it might be installed into a socket rather than soldered. You want to get the SAME part number of controller as OE installed. You have to transfer the prom. Do not change the prom on a metal surface nor on a carpet. Use a piece of wood and touch both metal chassis together along with yourself. Remember static electricity? I would give the chassis to an electronic friend and watch him do it.
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The good news is that I have no coolant or oil leaks. The bad news is it did not start. I didn't crank it very long, however, the engine sounded like it was becoming more serious about starting.

It's been 45 mins. since I tried to start and there is still pressure in the fuel lines, don't know how much. I'm gonna run out in a bit and pick up a fuel line pressure gauge. I probably should have done this first. Anyhow.

From what I've been able to find out it is OBD I. I was expecting the code 12 but get no SES flashes at all, the light just stays on. I'll be really careful to ground myself and eliminate any static if I dive into it (the ECM). Autozone has a OBD1 scanner for $25, however, the fellow there said I'd get the same info with the jumper. I might just buy it and give it a try, what's another $25 (what am I saying, that's about the cost of a 10 gal. batch of ale I want to brew).

From what I've read the e-prom is soldered. I'll check whats available locally with the ECM while I'm out.

Right now I don't have the air filter hooked up, but I replaced it when this whole mess started, no major clogs, just one autumn leaf.

I think the next step is to re-read Haynes manual sections about Injectors and the ECM.

Thanks again for all of the valuable comments.
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the 25 dollar code reader probably isnt gonna do you much good if you cant ground the aldl conn out and get the light to flash...bummer, but i really think the comp went tits up...corse, i dont want you to spend your hard earned cake on my hunch, but not much else i can think of...did you check an injector for pulse???need a noid lite...they`re probably as much as the code reader you speak of, but money better spent for you at this time imo...
Okay, picked up a fuel line pressure gauge, should have done this earlier. Hooked it up and turned the key to the on position. The fuel pump ran and the pressure went to 47 psi then started to drop and was down to 42 psi in less than a minute and kept falling.

kustomwerker wrote: "if its a leaky inj, or fpr, the fuel pressure guage will peak when you turn on the key, and then drop...if everything`s good, it should hold pressure at the rail indefinately..."

So, (this is like finding lost shoes, they are always in the last place you look) I'm gonna focus in on the injectors.

(Autozone has pre-programmed ECM's for $125 BTW).

What is the best way to find out which one(s) is/are open. I'm thinking that if I pull 1 spark plug at a time I will get a pressure drop when i remove the plug that is associated with the leaky injector. Or do I need to read the resistance of each inj. Or do I use a screwdriver and listen while someone cranks the engine (really don't want to do this). If they are all open I'm thinking ECM.

Replacing the T-chain got me over the "I've never done that" hump. I'm not at all worried about replacing injectors now.

Thanks again!
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check the inj wires with a noid lite...see if you get a soft glow out of the shouldnt glow at all until you`re turning the car over...then you should get a "flash while turning over...the comp controlls a ground to the injs,so you should have power to them all, but no ground until the motor is spinning...if you have a glow, then you have a ground that shouldnt be there...that could be a comp prob, or a shorted wire, but by the ses lite thing you have going on, i`d say comp...the fpr will also bleed off, but you would only see that in 1 cyl...i believe the injectors on you8r car batch fire, so if all the plugs are wet, i`d suspect the inj`s being the leak...DO NOT check for injector pulse with an analog could cook the comp if it isnt needs to be done with dvom hooked up correctly, led penlite tester, or noidlite...last being the`re gettin there bro...
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Thanks kustomwerker,

I'll do the noid lite test tomorrow. I believe that the ign. coils batch fire, not sure about the injectors though.

Thank you,
Look at the injector wiring both sides. One wire will be black = power from the relay/fuse panel. Second wire is green, for one side of engine, pink for the other side. Check engine electrical schematic for sure.

The colored wire goes to the ECM and as kustom states, ECM places a low potential, and this difference in voltage opens the injector and it dispenses fuel. I would disconnect each injector and measure its coil resistance. All should be within an ohm or two against each other overall, 2-4 ohms, I think. If every plug is wet, I'd suspect the injectors are working.

Timing light flashing at the marks while cranking?
If injectors are working, I suspect ignition signal to the coils would be getting there also. The ECm takes the crank/cam sensor signal and splits it into two signals, inj & ign.

I would attempt to start with pedal to the floor, as if it were flooded.

I'm real concerned about no code 12 first and foremost. My Helms manual for my 88 Dually suggests ECM. Haynes manual suggests? Both power sources going to ECM?
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No timing light. (I'm short on diagnostic tools still)
About half the times that I've tried to start it I have been holding the pedal to the floor, haven't notice any changes in the way it cranks.
The no code 12 is really bugging me also. Haynes says to take it to a qualified dealer (Don't think that is gonna happen). Autozone said 2 day delivery on a new ECM. I think I'll go order it so it is here by Saturday (yah, it's bugging me that much).
In the mean time I'll pick up a noid lite and check the TPS, inj. resistance, and check out the crank & cam sensors.

edit: I have to put this car on hold for a few days. Something else came up that I have to take care of first. I'll check back in when I get back and before I try the things I wanted to try today.

Thank you all for the responses.
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Finally got back and have an update.

1. Injector resistances (all 6) were 12.1-12.3 ohms (Haynes rec. 11-14 ohms). I had no luck finding noid lites locally BTW. So, I assume inj's are okay (thank heavens).
2. The TPS checked out in the correct voltage range per Haynes.
3. The MAP checked out also.
4. Camshaft sensor responded as expected per Haynes.
5. I ordered a new ECM. It should be in on Wednesday afternoon.

That's pretty much it for now. I hope to run a compression test this afternoon and plug the injectors back in (BTW, the injectors are really tough to get to in this car).
I agree, if all the spark plugs are wet, its safe bet the injectors are good mechanically, and as you see, good ohm wise. However, you might do a leakdown test with pressure gauge on fuel rail. A rapid decline would mean a leaking injector.

I was looking at the other day and the site suggested GM used OBD 1.5 for 2 years, 94 & 95. Hmm, your Haynes reads? I guess what I'm saying is OBD I may not apply here.

Wedsnesday, hmm......
Wow, that is a PITA...

I did a search and found the odd '94 OBD 1.5 weard, what were they thinking stuff. (Everett, your link took me to a pic of a palm tree.)

Well, one way or another, I'll find out tomorrow if it is the ECM is the problem. I'll try and run a compression test tonight (if I get a chance) as you described and check the fuel pressure also.

Sorry about the palm tree link. But you can see it wasn't a long "empire."

Your Haynes suggests? (what operating system?)
Sorry, had the book right here when I posted last and forgot it.

Haynes manual states only "OBD". It does refer to "OBD II system, used on 1995 and 1996 models".

I have not seen any specific reference to "OBD I" in the manual I have. And it suggests taking the car to a qualified dealer/shop for diagnosis. It does give the trouble codes though.

No problem with the palm tree. I googled "OBD 1.5" and found lot of references. Some of the links that the ALDL jumper from gnd to diag. (A to B) doesn't work on late 94 and 95 GM models. However, I bought this car on March 17 1994 (St. Patricks day). Is this a late 94?

I would think it would be an early '94. If you have any OE hoses, or something OE with the car, there will be a date of mfg for the part, or a 4-digit date code, i.e., 9403, meaning 3rd week of 94.

Date of Mfg should be on the VIN sticker on door.
Well, I'm back with the latest updates.

Mfg'd on Feb, 1994.

New ECM installed and "flashed" per Autozone. Engine cranks but still no start. The new ECM also did not make the SES light flash. I've found a few tid-bits of info on this but nothing conclusive yet.

For my next trick I think I'll measure the compression and maybe try new crankshaft sensors (haynes doesn't give any diag to check them out).

BTW, the fuel pressure at the rail dropped from 48 to 22 psi in 75 mins. (0.34 psi/min) fairly consistantly.

Thanks again for your input.
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No leaking injectors.
Crankshaft sensor is a coil wrapped around a magnet. Ohmmeter should show some ohms for continuity and nothing (infinity) to ground/case. A very small AC voltage will be available as it cranks.

If plugs are wet with fuel, then I would think crank sensor is working as crank signal is used for injector timing and ignition timing.

Spark occurring at the right time? Borrow, beg, or steal a timing light.

Ever view engine cranking at night with no light? See sparks? Coil paks not broken or grounded?
Thank you Everett,

Just to let you know, I haven't given up yet, but am pretty discouraged right now. I pushed the car out of the garage because I have to replace the oil in my other 2 cars. I'll pick up a timing light as soon as I can and I'll take a good look at the engine in the dark (that's a suggestion). I probably won't do anything this weekend but hope to get back on it next week.

Again, thanks for all the help. It is greatly appreciated.
the noid lite suggestion was not to test the inj`s, but the wiring to shouldnt have pressure loss at the rail as far as i know...the fuel is going somewhere...and it seems to be finding its way into the unlikely that all 6 inj`s are leaking at once...hey everett, does this thing have a dis module???without looking at it, i dont know, but that would make the problem occur...unfortunately, i work on such a vast variety of cars, i cant tell what the hell is used on what yr car know it when i see it kinda thing...

thanks. I'll find a noid lite. This car has more sentimental value to it than any other vehicle I've owned (and there have been a lot).

I keep focusing on the way it quit running (maybe a mistake), but it just died in the middle of the road, like something broke. And what is a dis module?

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