87 XJ No fuel pump prime no start fixes itself?

Hey all, I have an 87 Cherokee 4 liter with a strange issue.

Three times now, the truck has flat-out died on me. The first two times were at idle at a light and in a parking lot, and the truck just shut off like I turned off the key. The third time (last night) it happened while driving around 25 through a residential area, started dying on me and I was barely able to get it off the road into a gas station.

All three times the truck refuses to restart. No fuel pump prime and the engine just spins. But if I disconnect the battery and let it sit awhile (not just a few minutes or an hour or so, has to pretty much be all night) she will fire back up.

I also seem to start experiencing loss of power in 3rd and 4th for awhile before this happens. Doesn't run rough or miss at idle, but on the highway I'll have to shift into 3rd just to keep it moving

Jumping the contacts on the fuel pump relay runs the pump fine, but I still get no start, I assume no spark but I have to check that.

I've read through a lot of posts here that mention the crank position sensor. I plan on trying to check that in the next couple days as the weather warms up. Biggest problem is that it's intermittent, and will run for days or a week or more without any issues.

Anyone have any other suggestions?

Thanks,

Jeff

Sounds like a heat related failure of the CKP (aka CPS). You could try spraying it with water with a water bottle, not a hose, when it won't start and see if that helps.

The lack of power is most likely not a related issue, the CKP is pretty much start/no start or run/no run.

Well I finally was able to replace the sensor the other day. Found out the top bolt was already loose enough that I couldn't even tell I had the socket on there, until I turned it a couple times and it fell out...so maybe that was the problem

Since replacing the sensor I have not had the no start/no prime problem again. However, the truck did die on me once while driving, and I was able to get it to restart after cranking for awhile, like I had run it out of gas. Also, I still have almost no power when driving, especially when it's warmed up. Fuel pressure is good with a gauge, at least while it's sitting in the driveway.

I also have a lot of exhaust rattling, so I'm thinking I might have to lose the converter and see if that improves things any.

wack that converter out of there! its as old as me! if its the original.

Uugh, ok long time since my last post.

Well I took the truck back to Midas, and they replaced the muffler which was full of converter guts. They also accidently dumped out the remaining guts of the converter, so I think everything is cleaned out now

So the jeep ran great for quite a while, then started slowly getting worse and worse. Finally it got to the point that it was backfiring and dying (and killing my new muffler in the process). Managed to get it back home before it died totally and refused to restart.

Replaced the O2 sensor and the truck fired right back up and ran great for months.

Skip ahead to the last week or so. We took the truck out to dinner, and it was pretty cold outside (like lower 40's to upper 30's). The truck didn't fire up on the first attempt, but turning the key off and back on and it fired up (like it was taking awhile to pressurize the fuel system). Did it again as we were leaving restaurant, and then died on us totally again. Could not get it to restart. Strong smell of gas under the hood.

Came back the next day (still fairly cold) and got the truck started. Drove about a mile and was getting on the highway and it completely died on me again. This time after sitting a couple minutes it fired back up and I was able to drive it about 10 miles home. Pulled into the parking spot and it was idling extremely rough, then it died on me again.

Now the temps are back up in the 60's and it seems to start up and idle ok, maybe a little loping and roughness. I let it warm up completely and sit there and idle for about 45 minutes and it didn't die. But I know if I drive it to work tomorrow it will leave me on the side of the highway

One other symptom I noticed is sometimes when I start it up it idles very high (around 2k rpm) for quite awhile before dropping off. But it wasn't doing this on the occasions that it died on me.

I'm thinking replacing the MAP sensor and maybe the fuel pressure regulator, but not sure if anyone had any other suggestions.

Sorry about the long post.

Jeff

Howdy!

Might I suggest testing instead of replacing parts?

Great link: http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm

Sounds like you have more than one problem.

Possible bad coolant temperature sensor--not telling the ECU that the engine is cold.

Possible leaking injector(s)--original injectors are two-piece pinched together metal and plastic bodies. They WILL eventually start leaking all over the engine, and when enough fuel has hit the hot exhaust you will have a "Flaming XJ" melt down. Fix is a set of Ford (Bosch) orange-top 19 lb injectors from a 3.8L and up Ford. Run you about $30 at the salvage yard, direct fit.

Renix XJs are DESPERATE for good grounds, in particular at the dipstick tube (ICM/ECU/o2 sensor--three somewhat important items) and the strap at the back of the head to the firewall. Renew those grounds!

After you examine those injectors, and have renewed those grounds, post back with your findings.

Joe,

I'll go back and check the grounds again, but I did do that as part of the original troubleshooting of the problem that was resolved by the CPS replacement.

On the injectors, they are currently not leaking. I did replace all the injector to head o-rings when I was getting the truck back to running condition, as several of them sprung major leaks. I do have my doubts about the regulator though, although fuel pressure tests when the vehicle is actually running showed the correct pressures (I believe 31psi when the vacuum is connected and 39psi disconnected? Can't remember but they matched what was in the manual).

Jeff

jmkendrick said:

Joe,

I'll go back and check the grounds again, but I did do that as part of the original troubleshooting of the problem that was resolved by the CPS replacement.

On the injectors, they are currently not leaking. I did replace all the injector to head o-rings when I was getting the truck back to running condition, as several of them sprung major leaks. I do have my doubts about the regulator though, although fuel pressure tests when the vehicle is actually running showed the correct pressures (I believe 31psi when the vacuum is connected and 39psi disconnected? Can't remember but they matched what was in the manual).

Jeff

Click to expand...

Your pressure would be right. Re-check the injectors and fuel rail, a heavy smell of raw fuel under the hood is an early warning. Use a very bright spotlight and check with the engine running. A small leak will evaporate the fuel on a hot engine and you won't see it in time.

I had very similar symptoms that turned out to be the fuel sending unit. Since you have good pressure at the fuel rail, it seems to be functioning fine, but maybe there is a problem with the wiring running to it that gives you your intermittent problem. You might want to check the wiring/ground that runs directly to your unit at the fuel tank.

For the gas smell, I think autozone has a fuel additive that works as an leak-test dye. Might make identifying the problem easier...