Starts without a problem but only runs for a few seconds and quits.
Fuel pump and filter changed. Had intermittent problem for years with this and cleaned connector on MAP sensor but that has no effect now. Can someone tell me if I can by-pass the sensor without damaging the electronics? Any suggestions would be helpful. Thanks.

 

If you give it gas while it's running does it still die?

 

With an 87, you have a "ballast resistor" somewhere on the firewall. Cream colored.
It's purpose is to reduce noise on the fuel pump circuit.

If this resistor is bad, the engine will start momentarily (as this resistor is bypassed when the key is turned all the way to the crank position), but then die as soon as the key is released.

To troubleshoot if this is your problem, get a small piece of wire and jumper the leads on this resistor, which then "bypasses" it. Safe to do and will tell you if this is the root cause or not.

This must be ruled in or out before looking elsewhere.

 

If I give it gas it doesn't matter, it still dies.
Thank you for the resistor information. Jeep service department just put in a new fuel pump and some emissions part, will have to research what that was. The car ran fine for a month, so I don't think it was anything they might have replaced. Will get more information. This site is great. Thanks again.

 

Change the crankshaft position sensor. it is cheap and mostly the cause to your problem. If it still doesnt work, check the ECU. try borrowing from your friend's xj. I did it and it works fine..Then get a rebuilt one or used one. Mine used to have similar problems.

 

It takes 2 minutes to jumper your ballast resistor. Simple things first. ALWAYS.

That resistor is directly in play.

If you put a fuel pressure gauge on the fuel rail and watch it as it starts and dies, it might confirm that the fuel pressure is dropping off.

 

i think the resistor only reduces the voltage to the pump then the relay takes over as demand changes for mor fuel