Im new to the forum, i bought a '99 D1 a few months ago. Much better than any jeep ive had.
A few days ago it would start and run for 5 seconds then stall. It became an intermittent problem- it would run no problem then just stall... start/stall.
i did a lot of searching on various LR websites. I started compiling tidbits of info from different posts, posts that went nowhere, OP's that ignored advise and just replaced parts...ect. This is a long post but i figured it might help someone else diag. their problem.
So... start/stall, no check engine light, 20psi fuel pressure
1 Replaced fuel filter- could not break the fittings loose even after PB blasting for 2 days. Grabbed a different fuel filter with nipples and used rubber hoses. Ordered a Fuel filter kit from AtlanticBritish.
2 Before the filter was connected i had a helper turn the key to ON. Pump primes, helper tries to start, Pump does nothing.
3 Check the fuel pump fuse(engine bayright side) and inertia switch (right side of firewall)-good.
4 Checked for Spark- I belive no fuel AND no spark could be a crankshaft position sensor. From what ive read if you have spark then its probably not the CKP.
5 Check for power at the pump. Pulled up the rear carpet, mangled the rusty cover plate. Backprobed the white and purple wire (Power) with a paperclip- key on 12.6V for a few seconds then zero. Should have power while cranking but i had nothing.
6 Check MULTIFUNCTION FUEL RELAY under hood. I am not sure which years have this. It is next to the fuses. I had 12.6V on one white/purple wire but not the other. Also checked with key on and while cranking- nothing. I could not find anything on how to bench test the relay. I did find a post on taking a utility knife cut around the edge and pop the cover off the base. Once inside i checked for any damage, burn marks. I lightly cleaned the contacts of each of the 3 relays. I re-installed the relay and the truck started and stayed running.
Just for reference while running i had 13-14V at both White/purple wire under the relay, and the same at the fuel pump.
Ordered a new multifunction relay from AtlanticBritish.
Drove the truck all day today and after a few hours it started doing it again, went right to the relay. With the truck running if i wiggle the smaller connector (even just a little bit)the truck stalls.
One of the tabs to hold the connector is broken, hopefully the new relay will solve this problem.

 

Sounds like you've tracked it down to a flaky relay or connector.. Fuel pressure sounds a bit low, should be 2.3 to 2.5 bar which is approx 33-36 psi. Voltage sounds fine as far as running vs non running.

 

WOW!! Great job on the diagnosis!!

 

Thanks !!!!!!!! Good job. My teen daugthers drive the D1 and they have been complaining about the car stalling at stop lights. There is no CK light on and when I have driven it, it has run normal. I replaced O2 sensors (then it had a ck light on and a code) replaced spark plugs and wires. Ck light went off but the intermitent problem of stalling persisted. I guess I am going to check the relays now. By the way, my fuel pump has less than 10K miles on it, so I don't suspect that. But I don't see how the relay would only affect when the car stops. If the relay is failing, it would produce some kind of misfire or something while the car is moving.

 

Since relay is an electrical device, the slightly higher voltage when speeded up may be making the difference, it might just take a fraction of a volt. Volts drop slightly when truck is at idle.

 

Installed my new relay and havent had any issues.
It seems like that fuel relay can intermittently cause problems, mine just seemed to be a loose connector- even the slightest movement caused the truck to stall.
I would invest in a fuel pressure guage and drive your daughters truck around untill stalls, and see what the fuel pressure is.
Also if you replaced the fuel pump, i assume you replaced the fuel filter- most people including me could barely blow thru the old filter.

 

Thanks Blackand....... that is a good idea. I do have a fuel pressure gauge, I am going to use it.