2MJ's neither stay runnin??????????

[jeepaholic]

I have an 87 and 88...both have been sitting for a while but they have before. crank run for a few seconds and cut off like you hit a kill switch...one of them cranks like a champ and does this...the other one does not crank so good and just spits and sputters then dies...perhaps the crankshaft sensor on the spittin/spudder but i just put a brand new one on it..gonna try another one on it in case i got a bad one....but the other one cranks runs good then dies....help me :wrench: I am so confused..oh both are 4.0/manual

[jimoshel]

Start, runs, dies is usually a fuel problem. Put a pressure gauge on the test port and see what the reading is. Should be around 30psi. No gauge? As soon as it dies push the core in on the test port. If you have good pressure it will squirt out. If there is no pressure it will just dribble. Use caution, fire hazard. Suggest holding a rag to catch the gas. If you have good pressure, then it's electrical. If they've been sitting awhile, sometimes crud builds up on the filter, pump, injectors. A good cleaning will take care of that.

[Eagle]

Start - run - die usually mean the ballast resistor for the fuel pump has died. The resistor get bypassed when starting, so the engine gets fuel when cranking, fires up, then when you release the key back the RUN position the circuit reverts to the ballast resistor ==> no more fuel, so it runs out what's in the rail, then dies.

[jimoshel]

Holy c***. Completely forgot about the BR. Good show Eagle.

[jeepaholic]

enlighten me...where the heck is the ballast resistor....and could this be the same problem for the one that barely cranks and spits/spudders??

[maddzz1]

The 87 might not have a ballast resistor.

[kro10000]

enlighten me...where the heck is the ballast resistor....and could this be the same problem for the one that barely cranks and spits/spudders??

It is a resistor mounted on the drivers side fender (easily viewed with the hood open) it drops power to the pump to reduce noise/extend pump life. I think it is right about 1.4 ohms

 

It is white, has a single bolt going through it, and has two wires attached.

[jeepaholic]

where am i gonna find this part....orielly and ozone both say not available...but they also act like I am speaking pig latin....

[Eagle]

True, the 87 won't have it unless it was retrofitted as a TSB.

 

You can bypass it. If you find it, just jumper the two wires together.

 

But they should have it. AutoZone has it: http://www.autozone.com/autozone/access ... ing=search

[kro10000]

They do have it, I work at O'Reillys, the part I used was a Borg Warner, I believe the part number was RU4

 

It isn't exactly the same, it is .2 ohms higher, but works fine. The resistor won't show up in the computer there, only paper catalogs

[jeepaholic]

the 87 and 88 were both the same...but fuel pump fixed both trucks..what are the odds of 2 at the same time going out.....replaced the 87 and it ran like a top....figured what the hey and replaced the 88....boom it ran too...