The jeep has a 350 700r4 conversion done by a tweaker years ago.

Ran great except on the top end. Kinda felt like it was starving for fuel.

I built the jeep.... put a genright tank in. Got it primed again and running mint.

It felt like it was out of gas one day when moving around the shop. Added more. Seemed ok... then it did it again and thought it was low on gas forgetting I put 5 gal in.

it would run intermitently... when it ran it was running mint.

Now it won't start or will only run for a few seconds... then shut off. When it runs it runs mint... then shuts off like it's not getting gas.

Sounds like the fuel pump or filter? Just swapped them yesterday for new higher pressure stuff. Got it primed and it fired up and ran mint for 10 mins.

Now it's doing the same shit again. Any ideas? Sounds real simple.....?

I would make sure the brain is tuned for that motor. I bought a Jimmy that came stock with a TBI motor so I never even gave it a second thought. The motor is a vortech and wasn't fueling well enough and would idle irradically and then shut off. If yours is a motor and brain from the same truck then you are probably ok there. You can check the idle air valve and TPS too.

You know i have the same problem with my 87 k5 blazer with a 350 700r4 but it just started doing it the other day. Mine wont even ideal unless i keep pressing on the gas even then it just sounds like its low on fuel but i put 3 gallons of midgrade in it, nothin doin. My guess was the fuel pump as well on mine just havent replaced it yet. Any other ideas people.

If the idle air control valve is old, it could be gummed up and need to be replaced. Someone will probably post up how to do it with a DMM.

Sounds like the fuel pump or filter? Just swapped them yesterday for new higher pressure stuff.
Why?
There is no high pressure stuff on a TBI. Higher volume maybe, if you are running a HP engine. The regulator is after the injectors and maintains the pressure constant.
Using a pressure gauge on the inlet side of the TBI would tell you if the fuel pump is dieing or the filter is plugged.
I recommend you still perform this test. The pressure should not change from idle to reving it to under load power braking it.
Most are set at about 13psi.

next.

You need to isolate if the problem is ignition or fuel.
The ECM will not fire the injectors unless it receives the signal from the distr to tell it the engine is turning and there is spark.

So when it dies, pull the coil wire or plug wire and see if there is a nice plue spark that jumps at least 1/2".

If not then you need to test the dist pick up and the ICM-ignition module.

Here is the testing procedures for the pick up and the coil.
The module can be taken to AZ for free testing, although their results are about 50% accurate.

http://www.autozone.com/az/cds/en_us/0900823d/80/08/5d/3a/0900823d80085d3a/repairInfoPages.htm

Not sure if the problem I am having is the same as yours but mine recently started dieing randomly. I finally tracked the problem down to the fuel pump relay turning off (I can hear / feel it clicking) I have no idea however whats telling it to turn off.

I have a friend who had the same type of problem. It was the oil sending unit if it fails it will shut the fuel pump off. He put an after market guage in it and it would not run after that. You must T the line and run a factory sending unit. As far as the fuel pump relay shutting off I think that it only works on start-up after the motor is running the computer takes over and sends power to the pump. You could try to hook the pump up directly to a battery and see if it will stay running. Hope this helps

Sounds to me like the ignition module in the dist. Module may be on its way out or there is corrosion on the bottom of it.

An engine needs compression, fuel, and spark. What doesn't it have?
First thing I would check is fuel pressure, and check for spark.
It could be the ignition module, or the pickup coil. You can ohm check the pickup coil pretty easy. It is the 2 wire connector on the bottom of the distributor. But to replace it you will need to remove and dissassemble the distributor.

it's a fuel issue of sorts. it's at a shop now. If I take a hot wire and jump the fuel pump for a bit it makes some noises then some other noises at the engine (can't be close enough to both to determine anything) then I can start it and it runs for a bit, then pulls that crap again. the fuel pump runs fine and the solenoids are working properly. Can't wait to see what this shop says.

Sounds to me like the ignition module in the dist. Module may be on its way out or there is corrosion on the bottom of it.

X2. My 92 TBI had the module go out and it seems like a fuel problem because the injectors are not being told to fire. My truck would run perfect and then just die. Let it sit and it would fire back up.

it's a fuel issue of sorts. it's at a shop now. If I take a hot wire and jump the fuel pump for a bit it makes some noises then some other noises at the engine (can't be close enough to both to determine anything) then I can start it and it runs for a bit, then pulls that crap again. the fuel pump runs fine and the solenoids are working properly. Can't wait to see what this shop says.

chances are when you jump the fuel pump it is priming the system like it does when the key is turned on and the system primes up to start.even
though the fuel syst. is sealed, pressure bleeds off after shut down,and must be around 13 to 18 psi.to run .Have some one turn the key on while you listen for the pump to prime up. It can be heard through the fuel filler hole .do this after the truck has a episode and dies.Then jump the pump from the battery,but leave it hooked up, now see if the pump and truck will run. If so start checking for power,working back from the pump.Also check for good grounds they can cause intermitent problems.check the fuel pump relay Ect.After the motor is running the ISO module in the dist. sends a signal to the injector drivers in the power train control module or brain, if you want a simple name for it.This in combination whith the throttle possition senser and on some motors A crank or cam possition senser this tells the PCM the motor is running and controls the injectors and fuel pump.The shop you took it to should be able to plug a scanner like snap on into th ALDL port under th dash and get real time data on the injector drivers,injector pulse and any missfire trouble codes that may be set in the PCU. Or you may have a power train control module going bad,the fact that you can let it cool off and it starts and runs fine,that is a classic symptom.And just for shits and giggles check the spark,it should be strong and blue and jump a good half inch to ground.

Not sure if the problem I am having is the same as yours but mine recently started dieing randomly. I finally tracked the problem down to the fuel pump relay turning off (I can hear / feel it clicking) I have no idea however whats telling it to turn off.
I just diagnosed the same issue on a friend's buggy, turned out to be corrosion in the relay. New relay, no problem.

it's a fuel issue of sorts. it's at a shop now. If I take a hot wire and jump the fuel pump for a bit it makes some noises then some other noises at the engine (can't be close enough to both to determine anything) then I can start it and it runs for a bit, then pulls that crap again. the fuel pump runs fine and the solenoids are working properly. Can't wait to see what this shop says.

chances are when you jump the fuel pump it is priming the system like it does when the key is turned on and the system primes up to start.even
though the fuel syst. is sealed, pressure bleeds off after shut down,and must be around 13 to 18 psi.to run .Have some one turn the key on while you listen for the pump to prime up. It can be heard through the fuel filler hole .do this after the truck has a episode and dies.Then jump the pump from the battery,but leave it hooked up, now see if the pump and truck will run. If so start checking for power,working back from the pump.Also check for good grounds they can cause intermitent problems.check the fuel pump relay Ect.After the motor is running the ISO module in the dist. sends a signal to the injector drivers in the power train control module or brain, if you want a simple name for it.This in combination whith the throttle possition senser and on some motors A crank or cam possition senser this tells the PCM the motor is running and controls the injectors and fuel pump.The shop you took it to should be able to plug a scanner like snap on into th ALDL port under th dash and get real time data on the injector drivers,injector pulse and any missfire trouble codes that may be set in the PCU. Or you may have a power train control module going bad,the fact that you can let it cool off and it starts and runs fine,that is a classic symptom.And just for shits and giggles check the spark,it should be strong and blue and jump a good half inch to ground.

So here's the latest.

The mechanics that were all too smart to hear what I had to say "fixed" it.

It ran for 8 mins from their shop to mine. Then started and pulled into my shop friday.

Today I go to start it and it's running tits until it goes off cold idle... then it falls on its face and dies.

I can't wait to talk to these guys tomorrow. "SO NOW ARE YOU GOING TO FUCKING LISTEN TO ME OR DID YOU WANT TO SPEND ANOTHER WEEK TRYING TO BE SMARTER THAN ME?"

IAC valve....CTS have these been looked at or changed. Just a note...for these items and ignition I typically stick with AC Delco. I've used aftermarket before and just don't get the same quality/longevity from them..... .02

IAC valve....CTS have these been looked at or changed. Just a note...for these items and ignition I typically stick with AC Delco. I've used aftermarket before and just don't get the same quality/longevity from them..... .02

thanks... what's the IAC... and cts stand for. Sorry... I melt metal... don't know parts :D

oh oh oh.... and even better... my damn jeep started doing the same thing. It's always run fine!

map sensors can react the same.

its a vacume sensor that after a bit kicks in, if its bad it would sputter and run poorly.

they can either leak vacume or the elecs fail, also chech the line to it, if it cracks and they often do you have a vac leak and it will cuase the same thing.


also is there coolant/water?

if it still has the stock tbi sensors a dry system will fualt like this before the motor over heats

IAC = Idle Air Control...on the pass. side of the TB (throttlebody)...a big hex thingy. It is basically a "choke" valve so to speak.

CTS = Coolant Temp Sensor...in the intake manifold. Tells the comp the temp of the coolant to aid in ajusting fuel rich/lean for cold start up or running temps.

I am sure these have been changed/tested as they are often a reason for a rough idle and or stall situation. The IAC at startup when cold should speed up the idle speed then back it down. It is "usually" full of carbon and can be cleaned out.

IAC = Idle Air Control...on the pass. side of the TB (throttlebody)...a big hex thingy. It is basically a "choke" valve so to speak.

CTS = Coolant Temp Sensor...in the intake manifold. Tells the comp the temp of the coolant to aid in ajusting fuel rich/lean for cold start up or running temps.

I am sure these have been changed/tested as they are often a reason for a rough idle and or stall situation. The IAC at startup when cold should speed up the idle speed then back it down. It is "usually" full of carbon and can be cleaned out.


that IAC... should it be able to move in and out by hand when you have it out of the tb? I pulled it out to see what the deal was... had some crap in it.. like grass and stuff lol. Didn't run when it put it back in. Only starts when it's dead cold. then it falls on its face.

map sensors can react the same.

its a vacume sensor that after a bit kicks in, if its bad it would sputter and run poorly.

they can either leak vacume or the elecs fail, also chech the line to it, if it cracks and they often do you have a vac leak and it will cuase the same thing.


also is there coolant/water?

if it still has the stock tbi sensors a dry system will fualt like this before the motor over heats

there is coolant I do have a vac leak at the brake booster... very slight. ran fine on many trips having forgot to replace the gromet.

the lines look good on that device you're talking about. think I should replace it?

try disconnecting the vac line and pluging it off, then try disconnecting the elec connection. either should result in a smooth running motor if its is the problem.

Some sources ............

http://www.autozone.com/az/cds/en_us/0900823d/80/17/0c/4b/0900823d80170c4b/repairInfoPages.htm

http://www.crankshaftcoalition.com/wiki/Idle_air_control_valve_overview

And regarding the CTS some info here (may be of some help and maybe not):

http://www.2carpros.com/makes/gmc/trucks.htm

Sounds like the fuel pump or filter? Just swapped them yesterday for new higher pressure stuff. Got it primed and it fired up and ran mint for 10 mins.

What do you call higher pressure stuff? Too much fuel pressure with TBI is not a good thing. Did you replace the filter before the fuel pump? Make sure it's the correct one. This first filter needs to be about 10 microns, any finer will cause problems like you describe...

ok so my personal jeep















was just out of gas.

It should have had 1/2 a tank when this happened... so it leads me to believe someone syphoned it while it sat on the trailer over night.

The jeep originally in question is just building air pressure in the line.... so it's pulling air rather than fuel. which wasn't the original problem but has definitely added to it. can't wait to see what happened when I get the tank out and redo the lines. I bet there's a crack in a flare.

What do you call higher pressure stuff? Too much fuel pressure with TBI is not a good thing. Did you replace the filter before the fuel pump? Make sure it's the correct one. This first filter needs to be about 10 microns, any finer will cause problems like you describe...

I have been running a high pressure pump in my TBI rig for a couple years now. The regulator in the tbi can easily handle high pressures..

I have been running a high pressure pump in my TBI rig for a couple years now. The regulator in the tbi can easily handle high pressures..

And if the pump is casing fuel pressure to be above the normal 11-15 PSI then your fueling is off. It may run just fine depending on how far off things are but in open loop it's likely going to be rich.....This has nothing to do with the regulator handling high pressures. Why on earth would you use a fuel pump that is out of spec for the application?

And if the pump is casing fuel pressure to be above the normal 11-15 PSI then your fueling is off. It may run just fine depending on how far off things are but in open loop it's likely going to be rich.....This has nothing to do with the regulator handling high pressures. Why on earth would you use a fuel pump that is out of spec for the application?

Fuel trim LT 123 ST 126


I call that workin fine since under a stock aplication thats what I commonly see...


And to add a side note--there is a stock aplication that ran the very same regulator assy and also runs a high pressure pump... Can you guess what aplication?

And to add--the pump I am running is a pump that just about every parts store carries (bullet style)--nothing fancy or special

So take what I have said for what its worth...

a 45psi pump is fine for tbi.... just sends it back the return. the reg should take care of anything over required. It ran just fine when it ran :D

It's fine so long as the pressure doesn't go higher. That's why I said "If the pump is causing pressure to be above normal". The regulator is what holds the pressure so it depends on the pump if it would be a problem........Don't think this has anything to do with your issue anyways.:laughing:

well it's fixed. removed the last section of steel braked line (covers) from the tweaker install..... and what we have is a line that would kind of collapse at a crack in the liner and pull air in but not spray any gas out. when I got it all the way out I finally found the problem. The weirdest shit happens to me when it's stuff I don't understand.

And to add a side note--there is a stock aplication that ran the very same regulator assy and also runs a high pressure pump... Can you guess what aplication?


1995 Big block only, 25 psi regulator. GM also started replacing some TBI pumps with TPI pumps, the regulator flows the excess back to the tank anyways. Makes less fuel pump stock fit more vehicles I guess.

Oh yeah, and do I win a cookie?

1995 Big block only, 25 psi regulator. GM also started replacing some TBI pumps with TPI pumps, the regulator flow the excess back to the tank anyways. Makes less fuel pump stock fit more vehicles I guess.

Some 94&95 trucks I believe ran at about 30 PSI..

Some 94&95 trucks I believe ran at about 30 PSI..

Nope, just the 1995 model year big block TBI. First time I worked on one I was freaked out by the fuel pressure. That was back when I was working on these trucks under warranty. 95 small blocks stayed with the lower pressure, as well as 94 back trucks.

Now 94 big block ran a higher pressure pump, but the regulator in the TBI was still the 9-13 psi one.

Oh yeah, and do I win a cookie?

Don't take any cookies from Crash, you don't know where they've been!:laughing:

Fuel pumps are positive displacement pumps. Their ratings are actually volumn capability. Pressure comes from restricting their flow. A higher volumn pump than is necessary will result in excessive pressure on the injectors if the regulator, and the fuel return circuit cannot adequately bypass the excess fuel.
I had running rich problems when I connected my 4.0L Jeep "high pressure" pump up to my SBC TBI system. The stock regulator would not bypass the excess fuel. I'm now using that same fuel pump to feed my MPFI system without issues, although my fuel pressure is at the minimum recommended by Edelbrock. The result is that my engine also runs slightly lean, indicated by high BLM's that are correcting the lean condition.

True, but the electric pumps have an internal bypass valve rated higher than the regulator. Most TBI pumps will only hit 15to 16 psi stock when dead headed. Yet many replacement pumps will reach a higher pressure when dead headed, I have seen up to 50 psi. Flow is relative to pressure, lower pressure, less flow.