Starts, Runs, Dies, repeat... 94 Runner 3.0

[Toyrod]

Starts, Runs, Dies, repeat... 94 Runner 3.0 SOLVED?

I'm trying to help a friend on his 94 Runner. It starts fine, runs for about 3 seconds, then dies. You can let it idle or wrap the piss out of it, either way it lasts about 3 seconds before it dies. He took it to a shop that replaced the fuel regulator for $300.00 which made no change. Their next idea was to replace the fuel pump for $400.00 to see if that would help. That's when I opened my mouth and made it my problem.

I read through some FAQs and it looked like the VAF might be the issue. I used a FSM and tested the VAF, voltage to the ECM and voltage to the VAF. Resistance readings of the VAF were within range. Voltage at the ECM was 11.5 and at the VAF was 4.99. VAF. EFI relay checked out fine. Fuel flow to the cold start injector was good but I had no way to check the pressure. Fuel filter was replaced at the shop and has a slight leak on the system side. If you engage the starter right before it dies, it will run for another 3 seconds. I did this several times in a row and kept it running. (A little tough on the starter and flywheel, I know)

I ran the codes and got a 14, 24, and 31. 31 relates to the VAF but it seemed to check out ok. The other 2 didn't seem significant.

I'm hoping someone else has had this problem and knows the fix off the top of their head. Meanwhile, I am going to continue to check the ECM against the FSM.

Thanks for any help, guidance, etc.

Brian

 

[WristPin]

check the fuel pump circuit.
the AFM's door is a switch that closes the circuit for the circuit opening relay, which turns on the fuel pump relay.

unbolt the cold start injector fuel line. maybe they are easy to get to on a V6. i dunno. it has been a privledge not to work on those bstagde engines.

this will be a messy job, only purpose it will serve is to verify function of the pump, not performance. you really need to check the pressure. spec is 44 pounds.

put the banjo in a hose point it into a bucket. turn the key on, put your hand in the door of the AFM by unsnapping it from the filter housing.

look for consistant flow. likley you have a fuel issue. air could be a cause too. but spark does not show sypmtoms like yours.

now leave all that hose the way it is, and then in the diagnostic port jump B to Fp. the results should be identical.

also check for air leaks. make sure the intake hose is tight. make sure all wire connections are tight.
look for disconnected booster hose, and any other vacuum hose. make sure the PCV aint clogged.

the way i integrated a pressure gauge was instead of cutting my OE hose, i got one off a honda. its the same. cut that in half, use a T fiting, and some rated FI hose and rated FI clamps. by soaking the hose in boiling water it will help get the hose on the T. then slapped it back on inline.

 

[inkpot]

Howdy! I don't have any experience with that setup, but I once had to troubleshoot a Camero that did nearly the same thing. After a long and unsuccessful month of weekends working on it, we found that the oil pressure sensor was bad. It shuts off the fuel pump after a few seconds if there is not enough oil pressure to run the engine safely. John

 

[WristPin]

this engine does not utilize the oil pressure gauge to turn off the engine.

it is a good idea, though.

 

[Toyrod]

I pulled the cold start fuel line off and jumped the +B to Fp. It flowed about a pint of fuel in 10 seconds from about a 3/32 port in the banjo fitting. No way to tell what the pressure was but with that much flow, I assumed it was enough to keep it running at idle.

Fuel pressure spec is 38-44 psi. Is it possible that the cold start injector can operate on defficient pressure and the main injectors wont?

I used a timing light on it when it was running because I suspected a weak coil. It continues to hit as it is dying. So again, I am assuming it is not a coil issue.

I considered a major vacuum leak but it wont run even when you rev it up to 2500 rpm. Just flat dies. Also, the whole hit the starter over and over and it keeps cycling the run-die thing.

I'm thinking that the main efi circuit is not functioning and that it is only running off the cold start injector. I am going to check the ECM circuits to the VAF circuit and other related EFI functions. If I can't find anything out of spec, I think I will replace the fuel pump and correct the leak in the fuel filter that the shop left me.

Thanks for the help and keep the suggestions coming.

Brian

 

[inkpot]

Howdy! It sounds like every time you turn the key, it re-sets a relay/breaker/logic circuit in the fuel management system. Put a meter on your hot lead to the fuel pump. Watch to see if it shuts off before or after the engine cuts out. John

 

[Ranski]

As you know there are many systems at work hear. I spent months chasing a similar problem. In the end it was a fuel pump that was slowly going bad.

The fuel pump would fire on iginition then shut off. Can someone put an ear next to the pump while the start the engine to see if it shuts off prior to the engine diening. Just a thought.

But like I said I spent alot of time chasing this down. First I was focusing on all the efi stuff like MAF, TPS, throttle body, blah, blah blah. Then on to EGR then finally the fuel system with the circuit, the injectors and fuel pressure regulator. Probably the most frustrating thing I have ever done.

Good Luck!

 

[WristPin]

I pulled the cold start fuel line off and jumped the +B to Fp. It flowed about a pint of fuel in 10 seconds from about a 3/32 port in the banjo fitting. No way to tell what the pressure was but with that much flow, I assumed it was enough to keep it running at idle.

Fuel pressure spec is 38-44 psi. Is it possible that the cold start injector can operate on defficient pressure and the main injectors wont?

I used a timing light on it when it was running because I suspected a weak coil. It continues to hit as it is dying. So again, I am assuming it is not a coil issue.

I considered a major vacuum leak but it wont run even when you rev it up to 2500 rpm. Just flat dies. Also, the whole hit the starter over and over and it keeps cycling the run-die thing.

I'm thinking that the main efi circuit is not functioning and that it is only running off the cold start injector. I am going to check the ECM circuits to the VAF circuit and other related EFI functions. If I can't find anything out of spec, I think I will replace the fuel pump and correct the leak in the fuel filter that the shop left me.

Thanks for the help and keep the suggestions coming.

Brian

the cold start injectors sole purpose in life is to give a quick blast of fuel when the enging is below operating temperature. that is it.

when the engine is running it does not operate whatsoever.

reason we test for fuel at that location is cause it is easier than testing for fuel than anywhere else.

I dont see why you have not already fixed the leaking filter. its kind of stupid to case a fuel problem when you have a problem you dont feel like fixin.

like I said. this is likely not a ignition issue. look on craigslist for a new pump. I have seen them go for $50 with the tank many many times.

 

[WristPin]

Howdy! It sounds like every time you turn the key, it re-sets a relay/breaker/logic circuit in the fuel management system. Put a meter on your hot lead to the fuel pump. Watch to see if it shuts off before or after the engine cuts out. John

there is no fuel logic system. the ECU has no idea that the fuel pump even exists. as I described earlier in my first post how the pump goes about switching on, its all based off the air flow meter.
the Fp terminal in the diagnostic port is connected inline with the pump. by hooking one end of a est light to the Fp terminal, and the other to ground, when the fuel pump is running the light will come on.

the ignition switch has two IG circuits. once they are on, they are on. nothing really gets reset when you turn it off. the AFM has the task of esentially closing the circuit. if the engine is reved to say 3500 rpm, the ignition switch turned off, and the pedal floored, the same AFM circuit will be closed, with the exception of the open in the IG switch.

 

[WristPin]

Can someone put an ear next to the pump while the start the engine to see if it shuts off prior to the engine diening. Just a thought.

this is not a bad idea. but it will be hard to hear it running. and the best way to transmit sound in a way like this would be to hold big stick to your ear and touch it to the source of sound.

instead of this, granted the pump is running, you can connect a test light to ground and the Fp terminal in the diagnostic port. when the pump runs the test light will illuminate.

 

[WristPin]

I really think your problem is in the air flow meter, the filter or the pump.

 

[Toyrod]

(quote) I dont see why you have not already fixed the leaking filter. its kind of stupid to case a fuel problem when you have a problem you dont feel like fixin.

Mostly principal. I should clarify that it is more of a drip than a leak. I was hoping find the fix somewhere else and then take it back to the original shop to have them fix the filter. They likely screwed up the line out and if I mess with it, that will be my problem too.

 

[WristPin]

(quote) I dont see why you have not already fixed the leaking filter. its kind of stupid to case a fuel problem when you have a problem you dont feel like fixin.

Mostly principal. I should clarify that it is more of a drip than a leak. I was hoping find the fix somewhere else and then take it back to the original shop to have them fix the filter. They likely screwed up the line out and if I mess with it, that will be my problem too.

i hear that. those filters are not fun to change. and so far it sounds like the shop is full of derelicts. you cant just throw parts at a vehicle in HOPES that it will fix it. it is possible its just loose. they do have to real tight. the banjo bolt has a lot of threads on it, and when any bolt gets cross threaded, you cant get it in too far, before it wont go any more. so if its just a drip, hopefully its just loose.

 

[Ranski]

this is not a bad idea. but it will be hard to hear it running.

I put a length of fuel line in my ear and taped the other end to the top of the fuel pump so that I could hear it while I sat in the drivers seat...

The lengths one will go when troubleshooting by yourself

 

[Toyrod]

I went through the ECM and checked everything that is related to the EFI operation. Everything at the ECM is within specs. Everthing on the VAF is within specs.

I timed how long it runs. 6 seconds at idle, not touching the throttle. 1 second with the throttle mashed to the floor. It gets to 3000 rpm. Exhaust smells way rich.

Tomorrow I'm going to order a fuel pump and tighten the filter. I will also be checking for blockages in the fuel line. I'm going to fix one thing at a time until I figure this thing out.

Still open to suggestions. And I know I should figure out a way to check the fuel pressure. I'll work on that too.

Thanks

 

[Toyrod]

As you know there are many systems at work hear. I spent months chasing a similar problem. In the end it was a fuel pump that was slowly going bad.

The fuel pump would fire on iginition then shut off. Can someone put an ear next to the pump while the start the engine to see if it shuts off prior to the engine diening. Just a thought.

But like I said I spent alot of time chasing this down. First I was focusing on all the efi stuff like MAF, TPS, throttle body, blah, blah blah. Then on to EGR then finally the fuel system with the circuit, the injectors and fuel pressure regulator. Probably the most frustrating thing I have ever done.

Good Luck!

Fuel pump continues to flow with ignition in the on position. Pint in 10 seconds. Just not sure if the pump is creating pressure.

Thanks for your input.
Brian

 

[hobiesbestfriend]

It has to be a line(wire) running somewhere between AFM and FuelPump, incl CPU. Assuming of course that you have remembered to attach the AFM harness to the AFM(I know, just covering all the bases). You can have the fuel pump power cutoff and it will do this because it still gets power initially to start then switches so possibly getting power from initial line and then switches to the dead one. I can't recall exactly how it all goes down, but it sounds like you're pretty much up to speed. on what is where, so just need to check those lines. They run under the passenger carpet where they come up through a grommet in the floor. My 2 pesos

EDIT: Sorry, just noted the 94 3.0 litre part. don't know, but might be substantially different then I described.

 

[Toyrod]

I read about the 2 separate signals to the fuel pump from the start and ignition circuits on the 22re's in the FAQ. I didn't find any reference to that for the 3.0. And, I think I have it eliminated because I verified that the pump flows fuel for at least 10 seconds with the key in the on position.

Every bit of input helps.
Thanks,
Brian

 

[2ndGenToyotaFan]

I had a similar problem last month... I have a 22RE, but it was a bad connection at the air flow meter. My connector had come off almost completely. If you haven't checked the connection there, I'd do it. Same run for 3 seconds then die...

 

[Toyrod]

Several responses have said to check the air flow meter and/or the connections. I checked the air flow meter with an ohm meter and the FSM. Also checked the signal from the ECM to the air flow meter. Not sure how to check the contacts from the wire harness to the air flow meter but the contacts on both sides look great. I will check all this again while I'm waiting for the pump.

Thanks,
Brian