snacob14 Posted April 3, 2011 Share Posted April 3, 2011 so, I finally have pressure at the fuel rail. But now it won't run. Bought this truck a while back and just now started messing with it. Initially had no fuel pressure. Now I have fuel pressure but I'm not getting any starting. I can prime it and keep priming it and it will run, but when I try to hit the accerator it just pops and cracks/stumbles and dies. The exhaust is a little smashed just below the header, but no narrower than a bout an inch and a half. I'm kinda at a loss on this one. Link to comment Share on other sites More sharing options...
tbrand Posted April 3, 2011 Share Posted April 3, 2011 Year? Motor? Have you checked your sensors? Link to comment Share on other sites More sharing options...
64 Cheyenne Posted April 3, 2011 Share Posted April 3, 2011 Bought this truck a while back and just now started messing with it. How long been sitting? Old gas maybe? Link to comment Share on other sites More sharing options...
snacob14 Posted April 3, 2011 Author Share Posted April 3, 2011 sorry, its a 91 6cyl, gas is fresh, its the same gas I'm using to prime it with. Which sensors shoudl I be checking? Link to comment Share on other sites More sharing options...
kro10000 Posted April 4, 2011 Share Posted April 4, 2011 Definitely check the CPS Link to comment Share on other sites More sharing options...
Myron Posted April 4, 2011 Share Posted April 4, 2011 How much pressure do you have? Link to comment Share on other sites More sharing options...
NewfieMJ Posted April 4, 2011 Share Posted April 4, 2011 How much pressure do you have? :agree: If you can prime it and it stays running , you have a fuel delivery issue . I would start with a new filter , but if that don't fix it , you need to "test" the fuel pressure . Probably need a new pump but before buying one , trace and check the fuel lines for kinks or damages . Good luck Link to comment Share on other sites More sharing options...
snacob14 Posted April 5, 2011 Author Share Posted April 5, 2011 I am getting 40psi during cranking. Link to comment Share on other sites More sharing options...
87Chief Posted April 5, 2011 Share Posted April 5, 2011 Check fuel injectors... Make sure you have enough ohms on the connection. Injectors might be dried up and not able to send fuel to the pistons. Link to comment Share on other sites More sharing options...
NewfieMJ Posted April 5, 2011 Share Posted April 5, 2011 Screwdriver to ear , other end on each injector , you should hear them click when they fire while cranking . Can you ? Link to comment Share on other sites More sharing options...
Myron Posted April 5, 2011 Share Posted April 5, 2011 My jeep would only rev slowly. If I went from idle to WOT, it fell on it's face. Check the vacuum line that runs from top of the tank if you have one. My 88 TBI 2.5 has it, and when I fixed it, would go from idle to WOT without starving. Link to comment Share on other sites More sharing options...
BlueMoon Posted April 5, 2011 Share Posted April 5, 2011 Howdy all, I'm not holding my breath but, I finally had a reasonably good day and borrowed a fuel pressure gauge for my "only runs on starter fluid" MJ. Actually, due to the results of my first test, I drove back to my napa store and swapped the first for another one. Same results. The meter didn't even budge. Nada Nil Zip...no pressure from my fuel pump. As before when I pressed the valve in the fuel port, gas was present. It just wasn't present with pressure. So, I'm talking with a friend about my Jeep's problems and ordering a new pump and filter and he says he happens to have a fuel pump out of a '96 Cherokee sitting at his home. QUESTION #1: Good folks that you all are here, I pose the question to you. Will this fuel pump work in my rig? Thanks, many thanks to all of you for any and all of your help on this problem of mine. As soon as I able able I will get my ride back "off-road again". Kinda a twist to the old song. And then.... I can start tackling the other issues, but at least she'll run agin.. QUESTION #2: Will some please CONFIRM if spark is confirmed to be present and our "only runs on starter fluid" MJs fuel pumps have no pressure the cps being at fault can be ruled out? Link to comment Share on other sites More sharing options...
jeepaholic Posted April 5, 2011 Share Posted April 5, 2011 the cherokee pump will not work(as far as i know)...yours sure sounds like what both my MJ's were doing...Replaced CPS, fuel filter, ballast resistor, and finally fuel pump...Waallaaah purrrrred like a kitten...So replaced the pump on MJ#2....Waaallllaaah purred like a kitten... :clapping: Link to comment Share on other sites More sharing options...
BlueMoon Posted April 5, 2011 Share Posted April 5, 2011 Sorry, wanted to add my cps resistance reads 232 on cold engine as I am unable to get it running and manual states 200+/-75 ohms on hot engine. Link to comment Share on other sites More sharing options...
BlueMoon Posted April 5, 2011 Share Posted April 5, 2011 Howdy again, I found this on another jeep site, it may help us on trouble shooting: I see that no one has offered-up the Distributor's sync sensor as a place to look -- I'll detail a few tips below -- The Sync sensor is used in combination with the CPS to determine just which piston is at TDC (the CPS can only show crank position and #1 and #6 are at TDC at the same time, one on compression and the other at exhaust)... If the data from the DistSync is ambigous or missing, the ECU will try to fire the #1 cylinder, every other time the TDC mark flys past the CPS - if the engine doesn't start, then it'll skip one of the TDC instances and try to fire #1 180* off from where it started before... This could be part of why you're getting good starts & bad starts. The Dist Sync signal does have a tendancy to drop it's ground reference and become unpredictable -- Leme type some thoughts: So the sync connector out of the dist is a round 3-position connector -- Pin A = Black - Ground - (chassis gound, both in the dist and for the harness - you can unplug the connector to check both grounds seperately - it's OK to add a chassis ground to this line) Pin B = Blue - Output - (to pin C16 of the ECU - should show about 5 volts static between Pin-B and Pin-C - connected to harness, key on, engine off) Pin C = Gray - Supply (should be about 7VDC from pin C5 of the ECU) While you're looking at the static voltage between Pin-B and Pin-C, if you crank the engine, you should be able to see the voltage fluctuate as the sensor rotates (qty=1 wiggle per rev, so it's not that impressive) I seem to remember the gray wire on Pin-C having a stripe as well... -- was just looking at a dist yesterday, but can't remember much more Link to comment Share on other sites More sharing options...
snacob14 Posted April 6, 2011 Author Share Posted April 6, 2011 ok, so I replaced cps, nothing. still cranking and not starting. AGain, when I check hte fuel pressure I'm good. I can use the bleeder on the fuel pressure gauge and keep it running. So, I'm assuming spark is good, and i'm getting good psi to the rail, so are the injectors my last option? is there a fuse for the injectors? Module? Link to comment Share on other sites More sharing options...
snacob14 Posted April 7, 2011 Author Share Posted April 7, 2011 ttt Link to comment Share on other sites More sharing options...
maddzz1 Posted April 7, 2011 Share Posted April 7, 2011 I thought you said the pressure test showed no pressure? Link to comment Share on other sites More sharing options...
snacob14 Posted April 8, 2011 Author Share Posted April 8, 2011 not in this post. It is showing about 40psi during cranking. Link to comment Share on other sites More sharing options...
NewfieMJ Posted April 8, 2011 Share Posted April 8, 2011 Have someone crank the engine , preferably 5 seconds . Screwdriver to ear , and on the injecter . You will hear it click if it's working . If you have long hair , tie it back :) I say 5 secs cause if this 91 is like the later modeled jeeps , the PCM will shut down fuel and spark if the signals are not recieved from certain sensors after 3 secs . I would certainly check every fuse , and possibly switch a relay or 2 out (ASD ?). I'll have to look in the morning at my 91 to evaluate which options are there , and then get back to you . Only other things on the list are the cam sensor(dist sync) already mentioned or bad capacitors in the PCM (a $5 radio shack fix) Link to comment Share on other sites More sharing options...
kro10000 Posted April 8, 2011 Share Posted April 8, 2011 ok, so I replaced cps, nothing. still cranking and not starting. AGain, when I check hte fuel pressure I'm good. I can use the bleeder on the fuel pressure gauge and keep it running. So, I'm assuming spark is good, and i'm getting good psi to the rail, so are the injectors my last option? is there a fuse for the injectors? Module? I doubt injectors are your issue, rent a noid light set from your local parts stores and plug it in to an injector plug. If it doesn't light up than the injectors aren't your problem. Something isn't right, there is a crank reference sensor in the distributor cap under the rotor. I'd check that, engine grounds, ecm grounds, and consider finding a spare ecm to plug in. Link to comment Share on other sites More sharing options...
maddzz1 Posted April 8, 2011 Share Posted April 8, 2011 not in this post. It is showing about 40psi during cranking. Sorry, It was Bluemoon. He added something about his truck into your thread and I thought it was you. Any chance your cat is clogged? Link to comment Share on other sites More sharing options...
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