I'm having some difficulties with my essentially stock 1992 LT1 (6 speed). I have not been able to start it for the last two days. When I turn the key it cranks but does not fire up. It is very reminiscent of when my ECU started to go about a year ago. I would think it was the ECU again except when the ECU went the following were different:
1) With the ECU the starting was intermittent and problems then increased in frequency, this happened all of a sudden and now won't start.
2) the ECU problems were associated with temperature and the engine/ECU being hot.
3) There are NO codes being thrown this time where as there were several pointing to the ECU when it went.
4) I can smell a lot gas when I try starting it now like it is flooded. As I understand it, when the ECU goes it does not communicate with the CCU upon start up and the injectors are turned off so there is no fuel present.
5) After cranking the engine sometimes tries to fire and lugs along for a couple seconds after I have turned off the key this time, this did not happen with the ECU.

I have tried what other posts have suggested with holding the petal to the floor during cranking in attempts to clear the cylinders prior trying to start the car. No success.

The car is stuck at my place of work so I can't do anything like check the plugs for spark etc. I will likely have to tow it to the garage next week as I do not have anywhere to work on it myself.

Does anyone have any suggestions as to the problem or other things I can try? My working diagnosis is that I somehow flooded the engine so bad that it now requires the assistance of a mechanic to get it going again. I would have thought the ECU or the opti to be the culprits but I would have expected some sort of codes with either one.

Any assistance would be appreciated.

Thanks

 

You need a timing light, Noid light (at parts store) or a 196 side marker light and two wires with insulated clip leads and two short pieces of wire to make connection to an injector harness plug, fuel pressure gauge. Engines require fuel and air and in the right ratio, spark and spark at the right time and in your case, the injectors have to be exercised.
Use the timing light to see if you have spark and spark at the right time during cranking. Connect the fuel pressure gauge on the shrader valve on the right side engine, end of the fuel rail. See if you have 35-42 psi and see if the pressure holds up for a long time with ign off. Rapid drop means stuck injector, defective check valve in the FP regulator. Put the noid or 196 lamp across an injector plug and crank engine. The light should pulse during cranking showing the injectors are being exercised.
Oh yeah, pull one of the plug wires, ground one clip lead wire and put the wire near the inside plug wire boot, you should easily get 1/2 inch snappy spark during a short crank.

 

Could be a CTS giving up? ECU gets wrong info from the Coolant Temp Sensor, thinking it´s icecold and flooding the engine. Dunno if you can check it easy, maybe someone here knows if you can ohm it?

 

jfb and vette079 thanks for the help. I was able to get one of the guys at work to look at my car today to see if I could get it started. No luck but I do have more info at least.

We pulled a plug and it was bone dry. It also had a nice spark. He also suggested trying ether in the intake to see if that would work. Probably one of these "" Anyways it ran momentarily on the ether suggesting that the rest of the cylinders are getting spark as well. We could definitely hear the fuel pump and could smell fuel but it did not seem to be getting into the cylinders. I'm thinking the injectors are not firing and I'm leaning toward an electrical problem? Although no codes were being thrown I thought I would try my old ECU just in case that was the culprit. No luck there. I also have tried both keys to make sure it isn't the VATS key and I have also checked the resistance on both keys to rule that out.

Would checking the fuel pump pressure still be of any benefit? How about checking the injectors individually during cranking? Either one I would have to get done at a mechanic which would mean getting the thing towed this week.

Any chance this is something electrical with the VATS? If I'm saying something that doesn't make sense or I'm going down the wrong path please don't hesitate to correct me.

Thanks again for taking the time to offer assistance.

 

Check the pressure. That allows you to rule out the pump, filter, etc.

 

hi
. heres what you need. get a ohm meter and pull off the injector wires. Check the injectors. if any are below 10ohms it has a dead short. leave that one off. if more than one is less than 10 leave that one off too. you can run on 6 injectors but not 5. If you have a dead short you are putting 12 volts through the injector and into the ecu through the ground wire that goes into the injector driver. Those multecs are not good injectors. If this is the problem let me know. If all the injectors are above 12 ohms then it might be the ecu again. But, this is happening so much with your symtoms.By any chance did you check the injector fuses? good luck

 

Replace the FP relay.

 

Commonly known as the change parts and hope technique.

 

Yeah, a part that is commonly known to be the first place to start.

 

Well, OK then.

Do as jon at FIC said plus try the other relays under the pass. side dashpanel.
The one in the middle is for the fuel pump. Wich ones are similar to the fuel pump relay I´m not quite sure of.
Cheapest way to start at least.
I recently helped someone fix a no start just by switching relay´s.

 

I'm slowly getting there.

I checked the resistance on the right bank of injectors and they all measured 12.3 or 12.4. I will check the other side tonight when I can get someone to hold a light for me so I can see what I'm doing better. I am in the process of purchasing a fuel pressure gauge. Hopefully can get that tested in the next couple of days.

I checked the fuses which are ok but it sounds like vette079 you are referring to a relay which I take to be one of those silver things on the right hand side of the fuse box. I did not check those and will look into that.

I recently took a recording a couple of weeks ago of the car while it was running. I reviewed the data to see if the memcal was running low, which has been suggested on other posts as a cause of failing injectors. Everything seemed fine and it often runs very close to 128.

Formul89, where is the FP relay? I can't seem to find that specific term in the FSM.

Speaking of the FSM, I pulled it out last night. You think I would have read it sooner. It seems to be guiding me down the same path as many of you have recommended.

 

Overview as per chart A-3 "Engine cranks but will not run"

1) no codes on ECM
2) check pass-key, keys are proper resistance and no code 41 nor 54
3) actual engine temp and CTS temp are the same. I just checked this with my laptop in the car. As I understand it, this rules out CTS as suggested by vette079.
4) TPS is confirmed at 0% at closed throttle. Again as per laptop.
5) RPM is indicated on laptop during cranking

6) Spark was checked on one plug and present.

7) 4 of 8 injectors were checked for resistance. Still need to check the other four. Also they need to be checked with test light while cranking. Is there a way to do this with a standard ohm meter????

8) next step would be to check the fuel pump pressure if the injectors are not ok.

Hopefully I am getting somewhere. Any and all advice is appreciated.

 

forget the fp relay, your oil pressure switch will provide power to the fuel pump (if the fp relay is shot) after reaching approx. 4 pounds oil pressure.

Nope, you need a noid light or a side marker lamp like jfb said.

And definetly get that fuel pressure guage on it.

 

You mean it doesn't say to replace the fuel pump relay first??

 

The FP relay is $9.50 at NAPA. It will go sooner or later. Replace it anyways.

Don't be cheap.

 

How much do the rest of the relays cost? You either don't or refuse to get it.

 

I don't think you do, other than the ability to **** on other peoples threads with your smug comments.

The fuel pressure relay costs $9.50 at NAPA.

The other three, which are the same exact relay, won't leave you stranded because they control the horn, courtesy lights and the fog lights.

Go look it up in your FSM, genius.

 

I certainly did not need an FSM to troubleshoot why my '94 took many tries to start:

 

If I follow that logic, then I may as well replace the MAF relay as well. It's cheap. When you lose the debate you resort to insults.

 

See? You still don't get it. By removing the relay and looking at it you were able to confirm it bad. You didn't just tell someone to go buy one sight unseen.