Help Jeep looses all power

87 Jeep Cherokee Laredo 4.0 If you have a fuel issue wouldn't your jeep cough and sputter before stalling? If it's electrical or ground could it just loose all power? I was able to put 900 miles on my new motor then it just died backing out one day and same day driving it dropped rpm's to zero and lost all power as if someone turned the key off but withing a couple of seconds gained power back and wouldn't do it again for awhile has got worse over time now it does it at idle,driving, cold or hot dosen't matter rpms drop and looses power and dosen't regain it most of the time it will crank right back up but I have had to wait a couple of minutes before it would start.Idles fine runs good just looses power. I have replaced the cps,ignition module, fuel pump,relays and distibutor the fuel injectors are less than a year old.I was thinking maybe a ground worked its way loose after installing new motor or maybe a wire shorting. Would like to hear if I should continue to replace sensors or start looking at electrical. I do plan on getting around to replacing all sensors but I just want my jeep running at this point.I have put everything on hold as I busted up my transfer case and it was the 242 and took a while to find a replacement darn things are hard to find.Now it's time to get back to the stalling problem, now it dosen't jerk, cough or sputter just stalls and ideals? Oh by the way when it got really bad I let it set up for a month, after the month put a new fuel pump on it wow drove almost 30 miles before it did it and it reagined power and got another 30 miles to the house and only did it one more time but the next day it is back to doing it within one minute of starting it, go figure.

Oh by the way the 87 does not have a check engine light and my jeep dealer no longer has the DRBII or equivalent for this old Renix so scanner is out.

87jeepster said:

Oh by the way the 87 does not have a check engine light and my jeep dealer no longer has the DRBII or equivalent for this old Renix so scanner is out.

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No check engine light.
Here's some pictures that may help you with your vacuum lines.
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Thanks! I just can't see where your fuel pressure regulator vacuum hooked up, almost looked like yours didn't even go to the intake vacuum fitting or maybe it's routed different, I was told it goes to the top port hole(has 3 holes on this fitting) on a 89 but mines a 87 not sure if it would be the same right now mine is hooked to one of the side port holes of this intake fitting.I was smart enough to take pics of all this and download but my computer crashed and they couldn't retrieve any of my pics, lost them all.

Also I noticed the very first time it ever stalled afterwards my oil pressure dropped some(went from 60pnds to 40 pnds on a new motor) as well as the alt. gauge and remained that way.Thou the alt gauge always has pulled down with the ac on even after I had the alt. rebuilt last year but it now only carrys the 40 pnds going down the road after it warms up.Thats why I was thinking ground or short.Also seems when it starts the stalling going down the road the temp gauge pops up to 210.This has a new open radiator system as well as the new hi-flow thermostat housing and thermostat, and just a new oem waterpump.Live in West Texas and it just ran to hot for a closed system.

87jeepster said:

Also I noticed the very first time it ever stalled afterwards my oil pressure dropped some(went from 60pnds to 40 pnds on a new motor) as well as the alt. gauge and remained that way.Thou the alt gauge always has pulled down with the ac on even after I had the alt. rebuilt last year but it now only carrys the 40 pnds going down the road after it warms up.Thats why I was thinking ground or short.Also seems when it starts the stalling going down the road the temp gauge pops up to 210.This has a new open radiator system as well as the new hi-flow thermostat housing and thermostat, and just a new oem waterpump.Live in West Texas and it just ran to hot for a closed system.

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Make sure you have the ground strap on the back of the head to the firewall.

I was told to do away with this cheap factory ground strap which is has been cleaned and is tight and go with a heay gauge wire instaed of the strap, has anyone done this?

87jeepster said:

I was told to do away with this cheap factory ground strap which is has been cleaned and is tight and go with a heay gauge wire instaed of the strap, has anyone done this?

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It can't hurt but if yours is good don't worry about it.
Have you changed the fuel filter, could you have gotten some bad fuel?

Well the day it started the problems I had filled up so the first thing was drained the fuel tank, replaced the fuel filter as thought I might have got bad gas, didn't help so went ahead and replaced fuel pump as it was quite old, didn't help either.I no after I filled up drove about 20 miles, parked and when I backed out was when it just died for the first time and it had never done this before then thats when all the stall loosing rpm's started

87jeepster said:

Well the day it started the problems I had filled up so the first thing was drained the fuel tank, replaced the fuel filter as thought I might have got bad gas, didn't help so went ahead and replaced fuel pump as it was quite old, didn't help either.I no after I filled up drove about 20 miles, parked and when I backed out was when it just died for the first time and it had never done this before then thats when all the stall loosing rpm's started

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The 87 xj in the pictures sat for 2 years with the same problem. I bought it for $50.00. The problem turned out the be the rear bump stop at some time pinched the wire to the fuel pump. I felt a lump on the wire and gave it a hard pull and in pulled it too. Is your fuel pump quiting? You should hear it running.

Yes I hear the fuel pump when I first turn on ignition runs for few seconds, thou I thought I use to hear the fuel pump relay click with the ignition on but don't hear anything now that was why I replaced all the relays. I do no when stalling started somewhere down the road I could hear lots of clattering coming from a relay in the pdc box so the mechanic said it was because of a bad ground so he hooked up another battery ground straight from the battery to the fender well. I was out of town when this all started and on a Sunday at that only mechanic I could find open, anyway that did stop the relay from clattering but it still lost power and stalled he just scratched his head said he had never seen this before thought it was electrical and he wasn't good at electrical.Town was like population of 800.
I did pile lots of groceries in the back that day in the parking lot at sams and that is where it died backing out I wonder if I didn't knock a wire loose that may have something to do with fuel pump.

Wow $50.00 I have looked for a 87 to buy for parts haven't found one yet hard to come by in Texas.

87jeepster said:

Yes I hear the fuel pump when I first turn on ignition runs for few seconds, thou I thought I use to hear the fuel pump relay click with the ignition on but don't hear anything now that was why I replaced all the relays. I do no when stalling started somewhere down the road I could hear lots of clattering coming from a relay in the pdc box so the mechanic said it was because of a bad ground so he hooked up another battery ground straight from the battery to the fender well. I was out of town when this all started and on a Sunday at that only mechanic I could find open, anyway that did stop the relay from clattering but it still lost power and stalled he just scratched his head said he had never seen this before thought it was electrical and he wasn't good at electrical.Town was like population of 800.
I did pile lots of groceries in the back that day in the parking lot at sams and that is where it died backing out I wonder if I didn't knock a wire loose that may have something to do with fuel pump.

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The relays get their ground from all different places, but they All get their power from the same place,(the big post on the starter relay), try cleaning those connections. Those wires are also your fuseable links and can break from vibration.

Did test all the fuseable wires and all are fine but I will go out and clean all the connections on the starter relay.

WOW may have found my problem got a email from one of the posters who has a 87 cherokee laredo same as mine.Says that my vacuum lines going to intake manifold fitting are hooked up wrong. It appears my fuel pressure regulator vacuum line is hooked up to what should be my intake air box vacuum.Who knows what all I have ruined if this is the case(Egr valve, fuel pressure regulator ect.) as I did have to drive it this way over 200 miles to get home on that Sunday and clearly not all mechanics are familar with these old renix systems and this girl wasn't going to even think about thumbing it

87jeepster said:

WOW may have found my problem got a email from one of the posters who has a 87 cherokee laredo same as mine.Says that my vacuum lines going to intake manifold fitting are hooked up wrong. It appears my fuel pressure regulator vacuum line is hooked up to what should be my intake air box vacuum.Who knows what all I have ruined if this is the case(Egr valve, fuel pressure regulator ect.) as I did have to drive it this way over 200 miles to get home on that Sunday and clearly not all mechanics are familar with these old renix systems and this girl wasn't going to even think about thumbing it

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Hooking the vacuum up wrong will not hurt anything or will it cause your problem. If it were the vacuum connections it would never have ran 200 miles and now will not stay running.

Well I was questioning how I got 100 miles with all the vacuum wrong and it ran fine for the first 100 miles at 78 mph at that.Now it does stall if left at idle but restarts yet I can drive a couple of blocks before it looses power again dies restart get a few more blocks, so it's driveable but yet not really. The post Office is a couple of blocks away so everytime I replaced something I would take it to check mail to see if it still did it, now there are times I can drive 3 or 4 miles before the first stall. That is why at times I thought it was fixed I haven't got to try and drive it around the block in a couple of weeks as new transfer case just got here and have to get it in, would wrong vacuum do this? Yet would it not showed up immediatly after I put them on wrong?

I don't have much experience with cars yet, but do it just because my ten year old is interested in it...so I might be giving you the wrong answer.
My wife's VW acted like that until recently (especially when the weather was humid). Did a tuneup and problem was solved.
HTH
Boris

Thanks, this is what is so frusterating as when installed the new motor replaced so many things plugs,wires,distributor,waterpump, ect. everything that would be replaced in a tune up is new even has injectors less than a year old. Yet we have pulled motor, transmission ect. all at the same time so everything under the hood has been touched in one form or another makes it hard to isolate what we could have done wrong if anything