NEED HELP! '91 ram need diagnostic help!

[barbee6043]

no parts here for sale but hoping someome can help figure out what ails this beaast! its a '91 dodge ram 3/4 ton auto 360 tbi. 110,000 mi all original and stock, and has new coil and computer. . does this thing have a control box?? it will die and not get fire. sometimes will start sometomes gets no fire. replaced the guts of the distrubutor. are there any relays that can cause problem? does it have any sensprs to cause problem?? can the voltage gauge be trying to go out? any advice will be appreciated thanks BILL

 

[krazykuda]

Does it have the "old style" electroinc distributor? If yes, try checking the gap for the reluctor in the distributor. I had one in my old cuda that would start cold and not warm. Turned out the gap between the reluctor and the pickup was too wide at .030". I can't remember the spec anymore, but I believe it should be .007" or somewhere near there. The gap was enough to get spark cold, but when it warmed up and the gap opened up, it would not start.

Make sure you use a non-magnetic brass feeler gauge.

 

[fishy68]

Bill this is the for sale forum. You should post your problems in the technical forum so not to tie up space here.

 

[pettybludart]

I was gonna move this,but someone beat me too it?LOL

 

[RustyRatRod]

no parts here for sale but hoping someome can help figure out what ails this beaast! its a '91 dodge ram 3/4 ton auto 360 tbi. 110,000 mi all original and stock, and has new coil and computer. . does this thing have a control box??

Yes.

it will die and not get fire. sometimes will start sometomes gets no fire. replaced the guts of the distrubutor. are there any relays that can cause problem?

Yes.

does it have any sensprs to cause problem??

Yes.

can the voltage gauge be trying to go out?

Yes.

any advice will be appreciated thanks BILL

Take it in to a mechanic you trust.

 

[demon seed]

I was gonna move this,but someone beat me too it?LOL

You snooze you loose.:thumbup:

 

[camd64]

First thing would be to get yourself a factory service manual. From my quick search you do have a small cylindrical relay for the ignition and a crank position sensor. No old style control box though. Best thing is to get out a multi-meter or test light and start figuring what isn't getting power when it does die. Also sometimes you can do simple tricks like disconnecting the crank sensor and see if it will re-fire after it dies (some vehicles will go into a closed loop or kind of a limp mode that will bypass that sensors input) this may work on your setup. Check to make sure you have a good battery to start then go through the entire ign. system, make sure you wiggle the wires to check for any bad connections.

 

[RustyRatRod]

First thing I would do is locate the CEL, turn the ignition on, off, on, off and on. Watch the CEL. It will flash your trouble codes one at a time, three times each. When you see a code "555" come up, that means end of codes. You might wanna have a pen and pad handy.

 

[slantsixdan]

The SBEC (Single-Board Engine Controller) is located at the front of the driver side fender; you have to remove the battery to get at it. Find it by following the air cleaner snorkel duct; one end connects to the air cleaner and the other connects to the SBEC. Intake air is drawn through the SBEC housing to cool the computer. They rarely fail; it is probably not your problem, but it never hurts to inspect the 60-way unitized connector for corrosion or damaged/spread pins.

The distributor is not the ordinary Mopar electronic type with a reluctor and pickup coil. It uses a hall effect sensor. There is no mechanical or vacuum advance mechanism; all advance is handled by the SBEC. The hall effect sensor can get flaky with age and cause random stalling or no-starts followed shortly thereafter by perfect startup and fine running. The same can happen with a faulty hall effect sensor connector. But there is also the ASD relay, the fuel pump relay, the fuel pump, and other components that can cause this what you describe.

Go turn the ignition key on-off-on-off-on, leaving it in the "on" position and never going to the "start" position. Watch the "Check Engine" light. It will go on, then turn off, then flash out whatever trouble codes have been stored. Each code is 2 digits separated by a short pause. Each 2-digit code is separated from the previous code by a long pause.

So flash (pause) flash flash (long pause) flash (pause) flash (long pause) flash flash flash flash flash (pause) flash flash flash flash flash would decode as a 1 then a 2 for a "12", a 1 then a 1 for an "11", and a 5 then a 5 for a "55". Codes are not necessarily in ascending numeric order. "12" is "start of codes" and "55" is "end of codes". If all you get is a 12 and a 55, or just a 55, it means there are no stored codes.

The next time it fails to start, disconnect the battery negative cable for 60 seconds, then reconnect it, crank it unsuccessfully, then do the triple key flick and see what codes you get. In this case you're looking for that code 11, which means the SBEC has never seen a signal from the distributor (where "never" means "since the battery was most recently connected").

You really do need the factory service manual. The TBI system on these trucks is halfassed hardware sloppily controlled by halfassed firmware; everything has to be just right or the truck won't run well.

Your dash voltmeter is not causing your problem whether it's alive or dead.

 

[67cudafb]

I know this is a very old thread. I have never seen one of these pos until the other day had a guy I know call for advice. We talked on the phone and I kept telling him he had a bad ECU or a bad ballast resister. He kept saying that there wasn't anything like that on the fire wall. Finally jumped in the truck and ran over there and it blew my mind. The more I look online the more I find these things are just about impossible to trouble shoot. Hall effect crap :???: what the hell. Can't trouble shoot with a regular volt meter because voltage hits coil to fast to see #-o. What the hell was Mopar thinking with this. The worst part is this guy tries to rig stuff so the wiring on the truck is a mess. I feel bad for him as he doesn't have a pot to piss in. At this point I told him to look in the junk yard for a earlier truck to pull the dizzy and carb and fuel pump and wiring and try to convert it to something to get it back on the road. Anybody here done this before?