Hard Start/No Start Troubleshooting Log

[milehigreg]

I took my 89 out for a drive the day after I returned from vacation last week. Did about 40 minutes of highway driving then stopped at Walmart. Drove from Walmart to the Grocery store. Tried to leave. The car fired but then shut down after a few seconds. Had her towed home. By the way, I was VERY worried about the towing but it was relativley easy. There are two " T-slots" built into the front of the sub frame. Attached his cable with "t"s on the ends and pulled her up on the flatbed. He was careful and actually called another truck to get a couple of 4 X 4 lumber ramps so the front air dams didnt contact the truck bed.

Anyway, I have been slowly and patiently trouble shooting and thought instead of the usual plea for help that I would journal what I am doing. Those who want can review and provide confirmation and or advice.

It still does the fire up and then shut down routine. I have the sevice manual and have been pouring over the emissions and drivability section for trouble shooting procedures. I have also read the start sequence that gmjunkie keeps putting in posts about no-starts.

78,000 miles

There is pressue in the fuel rail.

There are no codes being thrown. ( Auto Xray 6000)

I checked the TPS and it read .636 volts with the throttle closed. This is out of spec so I adjusted it and thought well, that was easy. Still starts and then shuts down.

I disconnected the MAF sensor as suggested in the SM. Supposedly, if the MAF sensor is bad, the car will start and run on a defualt setting. No change.

Bought a fuel pressure gage at Harbor Freight ( on sale for $9.99 ). Checked fuel pressure. Only about 25 PSI. Had to stop.

Next step is to check the FPR. If that checks out then the fuel pump and or inlet screen. I replaced the fuel filter less than 10,000 miles ago so I don't suspect that. Do fuel pumps typically lose pressure when they go bad or just go out?

Here's the thing. You know how we all know that we should keep the fuel level in our tanks at least 1/4 tank? Well, since I hadn't driven her in about 3 weeks, I ran her down to about 1 gallon on my drive. My next stop was to be the Shell station for a fillup of fresh fuel. Could this have been the last straw for my fuel pump?

My last remaing check is the EGR. The SM says that an open EGR during starting can prevent running because the AFR is too high, ie too lean for cold start. No choke effect. I assume low fuel pressure prevents running for the same reason.

Junkie, did I read in some thread that you say to give the EGR a rap with a screwdriver to loosen up carbon deposits? I think the carbon deposits prevent the valve from opening though.

Well, what do you think? Am I doing this right? Do I correctly understand the concepts behind the the checks the SM is having me do?

Still smiling and praying I don't have a bad ECM!

[milehigreg]

Checked fuel pressure again last night. 25 PSI max with the key turned to the on position a couple of times. Pressure bleeds off slightly over 20 minutes.

I am now supposed to slowly squeeze off the fuel return line to isolate the problem to the fuel pump or pressure regulator. If the pressure goes up, FPR, if not, fuel pump. However, it looks to me like the fuel lines are hard piped. Wonder where I am supposed to squeeze?

Have to push it into the garage and get it in the air.

Also, located the fuel pump relay on the driver's side firewall. I'm supposed to apply 12 volts to the "A" terminal of the harness for the FPR test. Looks like I might have to remove the relay to be able to get to the harness.

Back at it tonight. c4c5, if your out there, a little confirmation would be appreciated.

[gmjunkie]

Nope,you didn't see where I said to Rap on the EGR to knock the carbon out!!I take them off and clean the carbon out and put a Stainless Screen in them!! The carbon will hold them OPEN and cause a BIG vacuum leak!!If it is the EGR you should be able to keep it running with the throttle,unless it has 1 Heck of a Big Chunk in it!! But that is Possible!! But 25lb fuel pressure is not enough!!My guess is either Pump (Good Suspect!!)or Pressure Regulator is bad or a Cracked vacuum line or fitting to the regulator!! PS.I've seen the short rubber hose on the pump in the tank develop a small hole or crack in it and not let the pump build enough pressure,(Recirculate in the tank) but still hold low pressure!! You should have around 36-42 lbs

[milehigreg]

Got the Vette pushed into the garage but spent last night removing the muffler from my son's 88 MR2. I brought it back to life with an engine swap last August.

Thanks for the response Junk. I will get it up on ramps tonight and try to find a place to squeeze off the return line.

Been shopping for parts. The fuel pump is cheaper than either the FPR or the EGR.

[gmjunkie]

Got the Vette pushed into the garage but spent last night removing the muffler from my son's 88 MR2. I brought it back to life with an engine swap last August.

Thanks for the response Junk. I will get it up on ramps tonight and try to find a place to squeeze off the return line.

Been shopping for parts. The fuel pump is cheaper than either the FPR or the EGR.

You don't have to raise it up!! You can go through the fuel Door!!! In Photo 5.5 the return line is #4

[vigman]

1) The engine will auto shut off of the oil pressure is to low ( or the sensor or wiring fail ).

2) I have had the resistor / rf trap in the fuel pump line FAIL 3X and have bypassed the WEAK design.

3) My Ignitor has gone out 2X due to a HP coil, but a stock trigger unit.


Back to basics....
1) Do you have spark when the engine is in this " no start " condition.

I want to clarify.. if the car will light EVERY TIME then shut down.. or will it light once then nada.

Vig~

[milehigreg]

Troubleshot down to the fuel pump and replaced it this weekend. Same behavior. Replacing the fuel pump is not diffucult at all.

There was mistake in the Service Manual though. To run the fuel pump with the engine off to test the pressure regulator, it says to apply 12 Volts to terminal "A" of the fuel pump relay harness. Didn't work. Looked at the wiring diagram and it was clear that it should be terminal "E". Did so, squezed off the return line ( Thanks Junk ) and the pressure didn't go up. Indicates bad fuel pump. It was running and making some pressure but not above 25 PSI.

Replaced the fuel pump and I now have a solid 40 to 45 PSI. The car still behaves the same way.

Vigman - As a matter of fact, it does fire only the first time I try it. Subsequent attempts don't catch at all. Does this lead us somewhere you have been before?

The gauge indicates 40 PSI of oil pressure. I have oil pressure but that doesn't mean the switch or the wiring or the connector isn't bad.

[gmjunkie]

I've encountered the VATS doing weird sheet like that!!!

[RWDsmoke]

The VATS can prevent the injectors from firing. That would be my guess. The oil pressure switch will not prevent the car from starting. It is only used power the fuel pump if the FP relay fails.

[milehigreg]

Took apart the dash this weekend and troubleshot the VATS Decoder Module. It is apparently operating properly. I get all the correct voltages. The trouble shooting procedures say that this points to the ECM!

I will keep the dash apart for now because I think it is more likely that there is something wrong in the HEI. Since it starts and then dies, I think something is preventing the switch over to ECM control after it fires. Ignition coil or ignition module. This from the reading I have been doing.

I will figure this out!!!

[milehigreg]

Replaced the ignition module with an inexpensive one from NAPA and still have the crank/catch/die behavior. This leaves the ECM as the culprit. Ordered a reconditioned one from Harris Performance in North Carolina through ebay just a few minutes ago.

Here's a recap of what I have done so far.

No Codes have been saved at any point in this now 5 week old exercise.

Fuel pressure was low so I have replaced the fuel pump. Not a difficult job. Done through the gas tank filler opening. Good fuel pressure now but that wasn't the problem.

Adjusted TPS sensor. It was out of spec but that wasn't the problem either.

Checked MAF sensor by disconnecting as stated in the service manual. If you disconnect , the ECM uses a default value and the car would run. Not the problem.

Removed the dashpad and breadbox and checked the VATS Decoder Module. Not the problem.

Checked the pickup coil as stated in the service manual by disconnecting the set timing connector. Not the problem.

Spoke to Alex here at Rocky Mountain Corvette. He concurs that it is probably now down to the ignition module or the ECM. He thinks ECM. Swapped igntion module this weekend. Not the problem. I did notice that the set timing connector plug inside the distributor was broken on one side allowing one of the connections to float a little. I put electical tape around it to make sure it wasn't shorting to the distributor case. Not the problem. I will replace the harness after I replace the ECM and it runs again.


I am learning boat loads about my car but I am ready for this to be over!

[ecss]

89's used Multec Injectors. The injector coils are exposed to the fuel. Over time the insulation of the coils wears away and the coils short out.

If your injectors are original (gray body color),

Remove each injector connector. Use an ohm meter and measure the resistance of each injector coil. Should be around 16 ohms.

A bad injector can cause the 3 other ones on the same circuit to malfunction.

[Drjohn]

I've encountered the VATS doing weird sheet like that!!!

I just lived that scenario.

Whover owned the car before me put in a VATS "bypass". Intermittently, the car would not start (just as if it didn't even have a battery). I would wait 20 minutes, and the car would start just fine.

I checked the wires on the steering column, and what I thought was the bypass looked to be taped together with just a piece of duct tape.

so... in an attempt to get another opinion, I had one of the guys in the speed shop at work take a look. He found the same thing. The previous owner, or his mechanic, had popped the resistor out of the key, and had duct taped the steering column wire to each side.

He soldered a new resistor in line, and now it is fine.

[milehigreg]

ecss - I have read that about the injectors somewhere else in this forum. A quick look at the wiring diagram shows that this is definitely possible. However, I don't think it is consistent with the behavior of my car - crank, catch, die. If one injector was shorted, the injectors wouldn't work and I don't think the engine would catch.

DrJohn - I have trobleshot the VATS system all the way through the VATS Decoder Module. It seems to be operating properly. If the problem is with the key, or the contacts, it will keep the car from turning over by locking out the starter enable relay. If the problem in is the VATS decoder module, it can either keep the starter enable relay locked out OR can lock out the injectors after startup through the fuel enable relay signal. This is what I was suspecting when I troubleshot the system. By the way, I graduated from high school in Campbellsville. My parents are from there and my Mom still lives there.

By the way, Geekinavette can program VATS right out of the PROM in your ECM. This is actually a better solution than the bypass. The bybass only bypasses the key resistor/contacts circuit. If the VATS decoder module goes bad it will still keep the car from starting/running. Removing it from the programming eliminates it completely. Do I have that right Bill?

[Drjohn]

ecss - I have read that about the injectors somewhere else in this forum. A quick look at the wiring diagram shows that this is definitely possible. However, I don't think it is consistent with the behavior of my car - crank, catch, die. If one injector was shorted, the injectors wouldn't work and I don't think the engine would catch.

DrJohn - I have trobleshot the VATS system all the way through the VATS Decoder Module. It seems to be operating properly. If the problem is with the key, or the contacts, it will keep the car from turning over by locking out the starter enable relay. If the problem in is the VATS decoder module, it can either keep the starter enable relay locked out OR can lock out the injectors after startup through the fuel enable relay signal. This is what I was suspecting when I troubleshot the system. By the way, I graduated from high school in Campbellsville. My parents are from there and my Mom still lives there.

By the way, Geekinavette can program VATS right out of the PROM in your ECM. This is actually a better solution than the bypass. The bybass only bypasses the key resistor/contacts circuit. If the VATS decoder module goes bad it will still keep the car from starting/running. Removing it from the programming eliminates it completely. Do I have that right Bill?

Just wanted to mention it. Some of the symptoms I had even when the VATS didn't enable were pointing to a computer issue (flashing "SYS" message, etc.). Seems fine now. I may actually program it out later. For now, I'm gonna run it, and enjoy actually starting it regularly

I've been in Kentucky for about 5 years now, so I'm still learning where places are.