92 FJ80 fires, but won't start

[TahoeCruiserGirl]

I have a 92 FJ80 that sometimes starts at first but then dies ( when it's cold ) and after that it won't re-fire. the starter turns the engine over but it won't fire up. After it sits for awhile though, it will usually start right up and runs great like nothing is wrong... I've had a mechanic look at it and he's found nothing wrong with it. He thought it was the fuel pump at first, now he says it's not... I added Seafoam to the gas and oil, it now runs better than ever... except of course when it won't start... Very frustrated I'm a single mom and this is my daily driver... I also have an 83 FJ60, I'll save my issues with that for later when I get my 80 figured out

Anyone have any thoughts?

 

[Michael Hanson]

How did he determine the pump was good? MIke

 

[TahoeCruiserGirl]

Basically, I think he just loosened a bolt and said it was getting fuel LOL

 

[Michael Hanson]

If it didnt spray everwhere and soak him its not getting enough gas. 2 cents MIke

 

[TahoeCruiserGirl]

Thanks for your 2 cents Mike!
He started to think it was my MSD ignition, but doesn't seem to have clue...

Guess I need a 2nd opinion... Anyone know of someone in Tahoe that could help?

 

[Godwin]

Does the FJ80 have a fuel pressure regulator (FPR) like the FJ62? If so that's something to look at. The FPR in the 62s is notorious for causing sporadic starting and running problems.

 

[Eicca]

Does the FJ80 have a fuel pressure regulator (FPR) like the FJ62? If so that's something to look at. The FPR in the 62s is notorious for causing sporadic starting and running problems.

Flying-saucer-looking kind of thing on the front-of-the-car side of the intake manifold? I think that would be it. Although I haven't heard anything about FPR failures on the 80-series 3FE.

My guess would be centered around the air flow meter. The start-and-instantly-die behavior usually stems from the computer not receiving air flow data.

Welcome to the forum, by the way. My mom loved her 1992 FJ80... Until she upgraded to a 1999 UZJ100 and gave the 80 to me

 

[Tenzig Norgay]

Could be a bad temp sensor, causing the computer to shut the fuel pump down. I''ve had same exact symptoms(different vehicle), and they kept getting worse. This problem could be tricky, and may be any number of things, wish you luck. I love Tahoe, so beautiful

 

[Eicca]

Could be a bad temp sensor, causing the computer to shut the fuel pump down.

Doesn't seem likely to me. I mean, if that happened on the road, say you weren't watching your temps and suddenly the car just shut off.

 

[jonheld]

Tahoe,

Weren't we just discussing this on the 3FE list?
You need to verify if your CE light is on when you have the crank-no start. We can all speculate and throw out ideas, but some basic diagnosis needs to be done by you so we can all help.

FPR failures are typically hard starting when hot. Not to say that it can't happen, but it is unlikely to be the FPR.

If the truck runs fine and has good power when it is running properly, I would think that the fuel pump is fine. I would suspect the fuel pump logic and wiring before the fuel pump itself.

I gave you a link to my diagnostic flow chart which either you or your mechanic can use to help eliminate some possibilities, but this stuff is hard to diagnose over the web. No one is going to be able to tell you to replace the XYZ part and all your dreams will come true. We are all willing to help.

 

[TahoeCruiserGirl]

Thanks for the advice everyone... I'm thinking the fuel pump logic and wiring seems to make the most sense with what I've experienced so far...

Jon,

Thanks so much for the link on 3FE! I printed your diagnostic flow chart. I'm going to see if my mechanic is willing to take a look... He didn't seem to be open to Georg's advice, so it may be time for a new mechanic. I have a friend who's out of town till Wed who can help me out. I still have alot to learn, so I'm hoping to find someone who will teach me a little as they help me. Trying to get as much feedback as possible in the meantime. I just tried to start it and the CE light does come on... From everything I am hearing on here, 3FE and friends who have looked at it. It seems you are probably pointing me in the right direction. Thanks for your help! I'll let you know how it goes

 

[TahoeCruiserGirl]

Thanks again everyone... Looking forward to learning more from everyone on here... Tired of feeling like such a dumb girl as far as mechanics go. Ready to get my hands dirty and learn about my 80, then hoping to get my 60 off-road soon!

~Sandi

 

[badmuthatrucka]

Does anyone else think it could be the MSD parts? I know I had problems starting and running by using Bosch plugs, and many people have had problems with after-market wires, caps, and rotors.

That being said, I'm probably completely off-base in thinking that. Just thought I'd put in my two cents' worth.

Welcome to the forum, Sandi!

 

[jonheld]

If the CE light is on when it's supposed to be, then we can assume that the EFI circuitry is functioning correctly. The next step would be to verify spark at the plugs during a crank no start. If you have spark, then it must be fuel delivery. If you have fuel then it must be spark.
If you had both, then the engine would fire.

About 6 months ago, I was having some really hard starting when cold. Once she was running it ran fine. I verified spark and fuel and sat there scratching my head. I played around with fuel pressures and all sorts of dangly bits to no avail. I decided to start again from the beginning and pulled all of the ignition components apart. As soon as I looked at the distributor cap it all became clear. The coil wire had developed a resistive connection and melted the top of the cap and wire. It couldn't generate enough spark to fire the cold motor even though I was seeing spark at the plugs. Once I replaced the cap/rotor/coil wire, everything was just fine and has been fine ever since.

This is most likely not your problem but I would employ you to find a mechanic that always looks for the simple things first.

 

[Mark W]

Before you run off chasing various ideas thrown out by folks on the net, you need to determine a few basics.

When it dies and does not restart, does it have spark? (I expect it does, but you want to rule this out)

When it will not start/run, is the fuel pump running (or even getting current)?

To test if it is running, you can instert a jumper between the B+ and the Fp terminals in the diagnostic test module. This will cause the fuel pump to be energized anything the ignition is turned on. Climb in back, or open the gas cap and listen for a fain high pitched whining.

If you hear it, the the pump is running (and by default must be getting current). If you do not hear it running, you need to determine if it is getting current or not. pull the carpet loose by the tail gate and in the middle of the cargo area you will find an access hatch in the floor. Under there you will be able to use a test light on the power lead to the fuel pump to see if it is getting current.

If it is getting current and not running... bad pump. If it is getting current and running it may still not be pumping. Not common, but it can happen.

You can check this by removing the rubber return line from the hard metal lione that comes from the pressure regulator. When you turn the ignition on (with the jumper still in place) if the pump is pumping fuel you should see it coming out of this line. Strongly.

If the pump motor is running and there is not fuel coming out of the return line... bad pump.

If there is fuel coming out, then the pump is almost certainly not the problem. Almost.

Now check and see if the rig will start with the return line reattached and pinched closed. if it does... the problem is probably a bad pressure regulator. And yes, they can cause cold start problems too.

If the rig still will not start (fuel pump powered and running, fule flowing and return line clamped shut... and Spark verified to be provided...) it is possible thatthe injectors are not firing... but we will leave that for now...


If there was no power to the fuel pump, then you need to check the circuit opening relay. Bypass it with a jumper so that the fuel pump is powered directly from the power feed to the rely. If the pump runs this way, then the relay is the problem (common). If the pump still has no power, verify that the power lead to the really is energized. If it is... the problem is likely a bad wire or connection in between the relay and the pump. the harness runs through the left rear quarter panel and rut holes allowing moisture and road salt in there are a common cause of failed electricals in the tail end of the rig.

If the power feed to the relay is not energized, check the EFI fuse first.

Since the rig will not even start after it dies, it is unlikely that the AFM is causing fuel delivery problems. It may be preventing ignition, so again... make sure that you do have spark before chasing down fuel problems that might not exist.



Once you have worked through these tests, let us know what you have and we can take it further if the problem has not been located.


Mark...

 

[TahoeCruiserGirl]

Does anyone else think it could be the MSD parts? I know I had problems starting and running by using Bosch plugs, and many people have had problems with after-market wires, caps, and rotors.

That being said, I'm probably completely off-base in thinking that. Just thought I'd put in my two cents' worth.

Welcome to the forum, Sandi!

So, we've done a diagnostic and it IS the MSD... Any suggestions? My mechanic is not familiar with it and a friend of mine says MSD ignitions suck... Wondering if it's worth repairing, or will it continue to give me problems... Would prefer fixing it and saving the expense of a new one, but is it going to keep giving me issues?

 

[jonheld]

Just to be clear, there are 2 coils in the circuit opening relay. The first one is energized by the starter signal while cranking. The second one is energized by the opening of the flap in the AFM once the motor catches and the key is released. Either one fires the fuel pump.

If the motor catches then dies I would suspect that the flap on the AFM is stuck closed or there is a logic problem to the COR or the COR is faulty. I am not sure this is the case here.

 

[Mark W]

Just to be clear, there are 2 coils in the circuit opening relay. The first one is energized by the starter signal while cranking. The second one is energized by the opening of the flap in the AFM once the motor catches and the key is released. Either one fires the fuel pump.

If the motor catches then dies I would suspect that the flap on the AFM is stuck closed or there is a logic problem to the COR or the COR is faulty. I am not sure this is the case here.

Could even be a simple as the AFM is unplugged. I have seen that plug come loose on bumpy roads when the wire retainer was damaged.

Mark...

 

[Mark W]

So, we've done a diagnostic and it IS the MSD... Any suggestions? My mechanic is not familiar with it and a friend of mine says MSD ignitions suck... Wondering if it's worth repairing, or will it continue to give me problems... Would prefer fixing it and saving the expense of a new one, but is it going to keep giving me issues?

I am unsure why anyone would install an MSD ignition system on an otherwise stock 3FE in a daily driver '80

I would urge you to return to the OEM system. Should be able to find the parts used for a decent price.

BTW... before you assume the MSD is bad.. there is a chance that it is a poor ground. Double check that before you write it off.

I dealt with an OEM ignition system in an FJ80 once that had given three previous shops fits... they had thrown part after part at it (at the owner's expense of course) and not solved it.

It turned out to be no more than a loose mounting bracket for the coil and ignitor, creating a poor ground.


Mark...

 

[jonheld]

Shortly after the release of the 80 Series there were all sorts of claims of increased power coming from MSD and Jacobs and one other one I forgot. I walked down that dangerous path early on. While the inital quality appears superior to OEM, the longevity is pathetic.

I understand why folks fall into that trap. I was quick to catch my mistakes at a significant cost of both time and money.