F350 keeps stalling

[Big Bri]

I own a 96 f350 with a 351, and 5 speed. its a commercial truck so its the old obd l. any way while driving at highway speed or sometime while accelerating the truck kinda stalls, more like you turn off the key but leave it in gear if that makes helps. any way if i let off the accelerator and ease back into it it will run fine for a mile or two and then do it again. I thought it was the fuel filter so i changed it, no help. then changed the pick up screen still no help. Any ideas?
like i said it's a 351 doesn't have the control module on the distributor, does have plug wires and one coil.
Thanks for any and all help
brian

 

[Diamondpilot]

Check the wires by misting water over the engine while its running at night. You can see sparks going to ground if bad. The real problem may be a dirty carb if equipped or a vacuum leak. I am really the last guy that should be posting. I have only owned 1 vehicle with a carb and only a couple with distributor caps.



Chris

 

[dodge man]

Sounds like the a fuel pump to me, but could be about anything, ignition, new coil?, new cap and rotor, carb rebuilt etc. I've had the fuel pump go bad on couple of vehicles of mine in the past and thats exactly what it did. It may be the old mechanical style on the side of the engine, which is fairly easy to fix. I don't know when Ford switched to fuel injection and electric fuel pumps.

 

[kennyd]

ANY vehicle from '96 on should be OBD2 per the feds...

The wires and distributor cap are a great place to start.

 

[Big Bri]

thanks for the replies, the truck is fuel injected, no carb. i have checked all the vac. lines and all look good. looked at the cap and rotor and both look ok. have not checked the wires yet. the fuel pump is in the tank and it been my experiance that when they go bad they go bad. the truck is obd l i know that for sure, seems like in 96 commercial trucks (this is a cab and chassis 12' flat bed stake body) did not have to run obd ll. i run into this every time i get my brake or inspection sticker (in louisiana they check the computer) any way when i took it to a shop to have them run the codes they told me they couldn't find the plug, i told them it was an obd l but they would not listen.

i'll check the wires in the shed but i've run a truck with a burnt wire before, a little miss but not a total stall.

thank for the help
brian

 

[kennyd]

Your are right...I glossed right over the "commercial truck" thing...

 

[Bill_C]

Actually its a vehicle weight rating loophole (not the commercial rating) that allowed Ford to build their F250's and up without being fully OBDII compliant. Sometime in the 2001/2002 time frame I believe they finally went all the way to OBDII. The trucks will have an OBDII connector but (at least on the diesels) most scanners will just go "huh?" You may be luckier with a gasser, a scanner may work.

 

[tractorsanmore]

Has the tps ( throttle position sensor ) ever been changed . Had a truck act like it was staving for fuel and that's what ended up fixing it .

 

[tommu56]

Does it have a variable ventrie carb? I had a 351 in a 83 bronco with one and the fuel pump went and acted the same way fuel pump was on the motor not in the tank.

tom

I should have read the rest of the thread you said fule injected and pump in the tank

sorry

 

[Big Bri]

Has the tps ( throttle position sensor ) ever been changed . Had a truck act like it was staving for fuel and that's what ended up fixing it .

i had looked at it, checked the voltage going to it and it was 1.004 volts, i think that about where it should be. i don't know any other way of checking them do you?

 

[skipmarcy]

i had looked at it, checked the voltage going to it and it was 1.004 volts, i think that about where it should be. i don't know any other way of checking them do you?

Reference voltage on a TPS is 5 vdc. You need a lab scope to do a sweep to check for dropouts or spikes in a TPS. Alot of Ford trucks didn't have the ignition module mounted on the distributor, it is remote mounted on an inner fender or firewall in a heat sink fixture. Use a timing light with long leads and bring it inside the truck with you and drive it - you can put the pickup on the coil wire and see if primary ignition (coil) is breaking down or put it on a spark plug wire and check for secondary ignition (cap & rotor) break down - the light will quit if ignition is crapping-out and it's bright enough you can still watch the road OK and see if the light is quitting while you drive.

 

[tractorsanmore]

Yes reference v is 5 . Idle is .5 to 1 v ( .9 best ) wot 4.5 to 5 v . You could remove throttle body and check the sweep with ohm meter , old one with the sweeping arm would work better

 

[Big Bri]

Reference voltage on a TPS is 5 vdc. You need a lab scope to do a sweep to check for dropouts or spikes in a TPS. Alot of Ford trucks didn't have the ignition module mounted on the distributor, it is remote mounted on an inner fender or firewall in a heat sink fixture. Use a timing light with long leads and bring it inside the truck with you and drive it - you can put the pickup on the coil wire and see if primary ignition (coil) is breaking down or put it on a spark plug wire and check for secondary ignition (cap & rotor) break down - the light will quit if ignition is crapping-out and it's bright enough you can still watch the road OK and see if the light is quitting while you drive.

very good idea with the timing light. i will try that tonight when i get home.
thank you!

 

[Big Bri]

Yes reference v is 5 . Idle is .5 to 1 v ( .9 best ) wot 4.5 to 5 v . You could remove throttle body and check the sweep with ohm meter , old one with the sweeping arm would work better

when i checked it it was key on engine off and i was not playing with the throttle. i will check that out tonight a W.O.T. and see what i get.

thanks for the info!

 

[tractorsanmore]

Voltage checks are key on engine off . Ohm checks are sensor unplugged ( you test sensor itself )

 

[roamrdb]

if you install a fuel pressure gauge and run it out from under the hood at the cowl, tape it to the windshield, you can watch the fuel pressure while you drive. i wouldn't use a rigged up one, but a proper setup because of fuel under pressure presents a real fire hazard. tps isnt likely to give symptoms you describe, but anything is possible, especially with your system. easy way to check tps is dvom on signal return line to ecm, what you are really looking for here isnt a carved in stone figure, but a signal that remains steady while your throttle is steady and changes accordingly, with no drop outs. your wide open throttle signal and idle signal should be within prescribed range. also, with a good scanner, ford has a self test, lots of times something will become apparent with self test. scanner will also allow you to drive and look at data including tps voltage. good luck

 

[Eagleview]

Loose low tension coil wire , chaffed tacho wire shorting to ground , distributor breaker/reluctor plate earth strap broken .

 

[irwin]

if you install a fuel pressure gauge and run it out from under the hood at the cowl, tape it to the windshield, you can watch the fuel pressure while you drive. i wouldn't use a rigged up one, but a proper setup because of fuel under pressure presents a real fire hazard.

Find a competent mechanic and see if any codes in system.. a good shop will be able to pull codes. OBDI systems should set a code for the TPS

You're losing either fuel pressure, injector pulse, or ignition signal...find out which one and then go to that system and test...if your losing fuel pressure most likely it's the pump (there are other possiblities )..injector pulse and ignition would be the module or the hall effect (inside distrib.)...good injector pulse but dropping ignition could be the coil or ignition components etc.

but... first things first.. are you losing fuel? spark? injector pulse?

 

[GATC35]

I'll place my bet on an in tank fuel pump. In the last year I have done my F-150 and two F-250's.

hey Bri...did you ever buy your wife the kitchen cabinets so you could buy a trailer?

 

[Big Bri]

sorry guys i haven't gotten out to check out the truck, between the rain, work, kids, and other honey do's i haven't had the time. will try all the tricks ya'll have left and get thing back going 100%.