1990 Cherokee Laredo fuel Pump
 

Hi, I have a 1990 Cherokee Laredo. I had the fuel pump replaced last month, Yesterday, I replaced the battery ground cable and now the fuel pump isn't working. I replaced the fuel relay, and it's still not working. Anyone have any suggestion?? it turns over strong, but it just won't start.

Unplug the connector to the pump and check the voltage. Also, you can check for fuel pressure by pushing at the Schrader valve in the fuel rail.

Thank you I'll give that a try..

Start at the beginning. Pull the Fuel Pump Relay and probe 30 in the relay socket. It should be hot all the time.

https://cimg0.ibsrv.net/gimg/www.che...33f485b30b.jpg

Keep this handy. You might need it.

http://jeep.avtograd.ru/cherokee/inj.../89jeepefi.pdf

Make sure you're testing the right relay. There is misinformation out there about which is which:

https://cimg2.ibsrv.net/gimg/www.che...6ee267a0c.jpeg

Check all the relays to be sure. Check the crank position sensor.

Check the wiring for shorts especially stuff near the exhaust system like the oxygen sensor. Look for workarounds that POs might have done.

Also as much of the wiring as you can at the fuel pump for poor contacts, breaks and shorts.

Still got the old fuel pump?

Since this problem happened after fiddling with grounds, check all the grounds. Read the cruiser tips:

http://cruiser54.com/

Exactly. You touched something. Something broke. Recheck your work before you chase anything else.

Okay, First off, the schematic is wayyy over my head. I have a working knowledge of car machanics but I am by no means a mechanic.. lol.. From your image of the relays, I replaced the power latch relay instead of the fuel pump relay although the auto parts store said it is the fuel pump relay, I'll have to check and see if it fits in the same space your image is showing. I replaced the fuel pump and filter last month. I'll check the cable again but I feel comfortable with the ground connection, I can hear the additional power in the crank now that its replaced. I drove the jeep to the auto parts, got the new ground cable replaced it and cranked the car and the fuel pump didn't start. I'll check the fuel pump connection but as I said, I drove it, parked it, changed the ground wire and suddenly the fuel pump isn't working. Thank you for your help with the diagrams, the relay one is different from the one I found online. I'll keep you updated.

Hi Dave51, Okay, I switched the relays and went back to ground wire, took it off, cleaned around the bolt a bit and put it back on, now I an hear the fuel pump turn on but its still acting like its not getting fuel... I've been having fuel issues since I first got the jeep. When there is an extreme temp change from cold to hot vise versa, I have to tap on the fuel rail like there's a vacuum, just tap on the rail and it would turn right over, but that little trick isn't working now. it just cranks like its not getting fuel. Any ideas??

Press that Schrader valve to see if gas comes flying out as per gat. May need to measure the actual pressure later. Check the plugs to see if they have spark. Got a multimeter? Check the fuel injectors to see if they have power. Pull the plugs to see what they look like, especially if they are like totally fried, wet with gas, black, whatever. Feel comfortable about pulling the injectors? I think they're clogged but do that last.

Are all the relays good? I think if the bad relay is now in the Latch it won't start either.

Assuming the relay was bad to begin with.

Strong stream from the Schrader valve, I don't have a spark plug socket or a multimeter … I don't understand, all I did was take off the ground cable and put a new one on.. Frustrated... guess I'm off to Harbor Freight … Thank you...

Well, there does seem to be a history of something with the fuel system, so this isn't necessarily out of the blue.

This will be easy enough to narrow down. So you have enough fuel pressure up to the injectors. You'll need to check spark next. There's a couple ways to do this-- either pull a plug, have it grounded to the engine and turn the engine over and watch for the arc; pull a plug wire and place it close to the engine, turn the engine over and watch for spark; or when you pull the plugs and if they're soaked with gas you probably got no spark. BTW don't hold the plug wire while doing this, there's a LOT of volts there.

So if you have spark but the plugs are dry then it's on to testing the injectors. That tapping thing certainly points in that direction.

BTW did you check all the relays? Again, that Latch Relay could be a problem. It's like the equivalent of the later ASD (Ain't Starting Da-engine).

And go to cruiser's site and check ALL the grounds.

A little too early to go to crank position sensor.

If it was me....

Get a loaner fuel pressure gauge and check fuel pressure at rail.

Allow you to test pump and regulator and perform leak down test.

30 psi without regulator and 30 with if memory serves. Only have to remove vacuum hose from regulator to check.

Yes, there's a history that's what started the fuel pump and filter replacement, but if I've got good pressure in my fuel rail there's no vacuum. I got an inline spark checker and my plug socket and multimeter, I'm waiting for my neighbor to come turn the key for me to check spark. I'll let you know what I find... Thanks for the help.

I guess I'll just buy all new relays, it needs to be done anyway..

Did you have spark?
I don't think that it is likely, but unplug and replug the wire from the coil to the distributor's cap. If you brushed against that while feeding the negative cable to the block, then it could have uncoupled and prevent sparking.

I like to pour a teaspoon of gasoline into each cylinder thru the spark plug holes to test for spark. Sometimes it is very easy to do like on our older Cherokees.

Did you find that the positive lead from the battery didn't need changing also? I've found that positive corrodes before negative corrodes in my experience.

Well, replaced the coil, no spark at distributor, tracked back to the crankshaft position sensor, this had about 3" of bare wire so I got a new sensor and went after it, I now have a socket in the bellhousing and I'm screwed... Picture a 5'4" 120lb woman kicking and screaming... ughhh.

replaced the relays, put in new coil, tracked it back to crankshaft position sensor, about 3" of bare wire there so I got a new sensor and went after it, I now have a socket in my belhousing…. I don't know what I'm going to do now..

Pull the inspection plate off the front of the bell housing. While there may not be enough room to pull the socket out (depending on where it is right now), you may be able to see it and direct a string, wire, magnet. etc. to get a hold of it and pull it back out of the top.

If you can't see it, turn the engine over and it should drop into a more favorable position.

Or pull the starter off which will give you a larger escape route.

Also please note that I don't write multiple posts instead of a single, complete post just to get my post count up to get to the next level.

With a socket on the bolt of the harmonic balancer. If that's too hard pull the plugs out to relieve compression and try again.

After you get the socket out don't put the inspection plate back. This will be a good time to check the flexplate condition and flexplate bolts (not like now, but after you get the important stuff done).

LOL... I have no idea what you are talking about when you speak of post points, and I just became active on here so I didn't realize that each reply wasn't direct to person, just noticed that when I came back to check if anyone responded. I'm taking the day off and will start with the magnet to try and retrieve the socket then work from there. Glad this is happening in the summer so I'm not dealing with nasty weather while I'm doing this. God Bless and Happy Father's Day to all of you

You need to pull the inspection plate first. If you drop the magnet down there blindly it will just stick to the flywheel or flexplate. The inspection plate is only 4 bolts and will go quick and the socket may just be sitting right there. I believe it's too big to get by the flywheel but should be able to come out if you pull the starter. It's not a deep socket is it? IMO pulling it out from the top will only work if you can hook up your gimmick to the socket from down below (like the magnet should be between 2 strings so 2 people can move it up and down, or thread some twine through the socket -- the use of any retrieval gimmick will probably require 2 people).

If you can't get a gimmick to work in a couple of tries, it's probably best to pull the starter and pull it out that way.

OTOH, maybe it's sitting right there on top. Do you feel lucky?

Yeah, I thought I felt lucky but I was wrong... lol... got a magnetic flex rod and got it down in there but it didn't come out. Going to take the face plate off tomorrow and pray its right there. Got the sensor off though so that's progress.. God Bless my neighbor, he volunteered to help me check the spark and here we are... But I know my jeep is going to feel so much better when this is done... lol.. She's been a tough old girl up to this point, she deserves some TLC

Don't forget the cable to the starter is hot so disconnect the battery if you have to pull the starter (I think bolts will fit through that little space but not sockets-- guess we'll find out). You may have to bend the inspection plate a little to yank it out if you don't pull the starter (just something to consider if you're wondering why something that you think SHOULD happen, but doesn't).

At the least, inspect the flexplate for cracks and retighten the bolts. The "correct" way is

https://www.cherokeeforum.com/f51/ho...ocking-125547/

This is one of the places where you really should use a torque wrench. To prevent the engine from turning hold that bolt in the harmonic balancer with a socket and breaker bar.

Well, finally got the faceplate off last night, today I'll be fishing for socket... lol.. Pray for me...

just changed out the CPS and still have no start. already had gotten the socket out. just keeps cranking, but no start. Any suggestions to anything else I should look out for?

What do you think about the ems, the brain? Could I have shorted that out? I have 2 diagnostic relays what do I need to check those? or can I?

I assume you replaced the battery to block ground wire, there are other ground wires. You might double check that you put back all 4 wires back on that ground stud on the block. Sounds like your block stud is solid, but you could double check the stud on the motor block and make sure its not loose. I reinstalled that stud with blue loctite because it would come loose over time.

Just so you don't think your the only one pulling your hair out. I just had 2 parts go bad at the same time unrelated, alternator and idler pulley bearing. Alternator was whining and not charging, replaced it and the bad bearing whine was still there. Spent half a day deciding between ac compressor or idler pulley, $8 bearing sure sucked the day away.

Those diagnostic connectors are for a tool probably no one has anymore (well, one guy anyway).

Do you now have spark? What brand of CPS did you install? Did you pull the plugs to see what they look like?

You need to go to http://cruiser54.com/ and do tips 1-7. Note #7, even a new CPS could need tweaking.

Also #4 looks good. Shoot the parts cannon sparingly (although if CPS had bare wires that was probably a good move)(but it could have been tested beforehand)(and then just use electrical tape if it passed)(cause I am "frugal")("cheap").

Do the rotor and cap look OK?

And I am that one guy :D . Well besides Cruiser anyways, he probably has the original DRB something something whatever they called it. A snap on mt2500 with a jeep 1 connector is what is needed, the Solaris might work if the connector fits the communication wire. There is a guy that made a monitoring device he sells but it is live data only too. Having said that, it is not any help in a no start situation, live data only, no ability to throw codes from a bad sensor. Renix is even pre OBD1. I believe 91 to 95 is considered OBD1. We renix guys and gals have to go old school and test with a multimeter.

To OP, i should mention you can test to see if the injectors are firing fuel a few different ways so you eliminate the fuel as a problem. You can use a stethoscope or piece of vacuum hose held to your ear on each injector and listen for a click at each firing. You can pull a spark plug and see if its wet with fuel. You can buy a noid light, it plugs into injector and then plugs into injector wire. It will light up at each pulse.