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87 4.0 won't start

T

the_bandit87

NAXJA Forum User
Location
Sydney,NS
Well, the other day, I drove my XJ out of my garage, and parked it on a hill in my yard. It was at a pretty steep angle, and I left it there for about 2 hours in the hot sun. Well when I went to start it, it cranks over fast and fine, but it will not catch. My fuel pump has just started to make a little noise as of late. Not only is it louder when the pump is initially cycled, but now you can hear a buzz while the jeep is running. Even though my pump is noisy, my first though was, "oh its just vapor lock" or somthing like that, because of the angle I parked it and and how hot it was. Well I coasted it back into the garage and, tried it the next day, same thing, it cranks but does not start. I checked the pressure relief valve (the one on the fuel rail right by the pressure regulator) and it is DRY, it will not spit out fuel like its supposed to when you open it. Later on I tested it for spark, which it has. Also there are two funny things I have noticed. Now when I cycle the pump (turn the key to the on position), right afterwords, I can hear a drip/gurgle, which I am sure is fuel driping back into the tank. The other thing is, after I crank the jeep over, I hear a BUZZ coming from the left hand side of the engine compartment (think the sound a pressure washer makes but quieter). It sounds almost like an electric pump, and all I can think it could be, is the pump for the windshield washer, but why would that start when I am cranking it? Shouldn't all power be drawn to the starter circut and associated engine electronics? In closing, I know for sure that the engine is not getting gas. I know that the fuel pump is kicking in, but I do not know weather or not it is even getting gas out of the tank. The other think I'm really not taking into account is some sort of electronic problem, bad sensor ect. I don't really have any evidence that this is could be the problem. Only other thing I can think of is that some how there was gunk in the tank and its clogging up the lines now. Tell me what you guys think.
 
the_bandit87 said:
Well, the other day, I drove my XJ out of my garage, and parked it on a hill in my yard. It was at a pretty steep angle, and I left it there for about 2 hours in the hot sun. Well when I went to start it, it cranks over fast and fine, but it will not catch. My fuel pump has just started to make a little noise as of late. Not only is it louder when the pump is initially cycled, but now you can hear a buzz while the jeep is running. Even though my pump is noisy, my first though was, "oh its just vapor lock" or somthing like that, because of the angle I parked it and and how hot it was. Well I coasted it back into the garage and, tried it the next day, same thing, it cranks but does not start. I checked the pressure relief valve (the one on the fuel rail right by the pressure regulator) and it is DRY, it will not spit out fuel like its supposed to when you open it. Later on I tested it for spark, which it has. Also there are two funny things I have noticed. Now when I cycle the pump (turn the key to the on position), right afterwords, I can hear a drip/gurgle, which I am sure is fuel driping back into the tank. The other thing is, after I crank the jeep over, I hear a BUZZ coming from the left hand side of the engine compartment (think the sound a pressure washer makes but quieter). It sounds almost like an electric pump, and all I can think it could be, is the pump for the windshield washer, but why would that start when I am cranking it? Shouldn't all power be drawn to the starter circut and associated engine electronics? In closing, I know for sure that the engine is not getting gas. I know that the fuel pump is kicking in, but I do not know weather or not it is even getting gas out of the tank. The other think I'm really not taking into account is some sort of electronic problem, bad sensor ect. I don't really have any evidence that this is could be the problem. Only other thing I can think of is that some how there was gunk in the tank and its clogging up the lines now. Tell me what you guys think.
Click to expand...

I think you may have a CPS (crankshaft position sensor) problem. Very, very common for the connector to fail and leave you cranking but no-start.

Sensor is mounted about 11 o'clock on the bellhousing drivers side. Follow the wires from that and locate th connector, give it a good re-seating and see if that helps. I eventually spliced the connector out of circuit and haven't had a problem in years.

Oh yeah, CPS resistance should measure between 200-300 ohms if you wish to check it that way but the connector is often the trouble and that test doesn't reveal it because of inadvertently re-seating the connector when checking the sensor.

BTW - don't have much for you about the noise but remember the IAC stepper motor operates for a few seconds after shutdown via the latch relay. IAC is mounted on the throttle body or TB.
 
XJXJ, read his post. He has no fuel pressure but has spark. If he has spark it is not the CPS.

If you can hear the fuel pump run but no fuel at the rail, it has to either be pump related or fuel line related. Pull the line before the fuel filter and see if you get fuel there. You may just have a plugged filter. If you still have no fuel pressure then you have a problem in the tank. I have seen the short hose that connects to the pump come off several times. Otherwise your fuel pump may be shot. The dripping type sound in the tank may be the check valve in the pump is bad, allowing the fuel to come back out the line, but that wouldn't cause no fuel pressure, only the inability to hold pressure.

My bet is on the short hose being off, but can't rule out the pump.
 
Thanks, I'm going to go and check both the CPS and the fuel lines. It has a new filter in it by the way, but I guess that wouldn't help having sudge in the tank. I'm thinking about a new tanks, because mine is pretty rusty and its stuck inside the skid plate. The bolts on the tank are frozen too, so I'd probably have to get new mounts welded up if I did drop the tank. I remember hearing alot about how much the CPS sucks in XJs, but honestly that never occured to me when I was trouble shooting it. Thanks again guys.
 
Sorry guys, my old bad eyes ran everything together and didn't notice the spark check. Check pressure at the Schrader valve but it would be best to do a volume check with a suitable container. Should pump a quart in 30 seconds easy.
 
Check all that, not only the fuel volume but the pressure. I made a fuel pressure testing gauge out of a piece of hydralic hose with a schraeder thread. Actually I think its from a air conditioner refill kit. I attached a simple pressue gauge I got at a hardware store to the hose. Cost was around $15. I think the fuel pressure should be around 35lbs with the key on.

One other thing to check is the starter relay. Its behind the battery under that cover for the fuse blocks. Check the connections and clean as needed. All the vehicle power goes through it. Wouldnt be surprised if it needs to be replaced, it's around $40. Sounds like what mine did a few years ago, replacing the starter relay fixed it.

Check the connections on the ignition module which is under the fuse blocks.

--Karl
 
Well I took off the fuel line that runs from the fuel tank to the filter. Then, after attaching a hose to the fuel line, and running the hose into a bucket, I cycled the fuel pump, and then cranked the engine over. I did get fuel flow into the bucket, but it was quite slow. I don't know weather its because of a weak fuel pump, or a because the flow was slowed because of the large diameter and length of the hose that routed the fuel into the bucket. I then took off the fuel filter and checked it. It was not clogged. All I can think of now is, either A: Somthing is clogged in the line between the fuel filter and the fuel rail (I'm not sure how this could happen since the fuel filter should pick up any debris) B: The Fuel filter is weak and is not making enough pressure to run the engine C: Some kind of electronic problem is stopping the injectors from firing.

I'm kind of puzzled here becasue I didn't think the pump would move fuel at all.
 
The small can shaped thing at the front of the fuel rail is a bypass pressure regulator, if it stuck all your pressure will be bypassed back to the tank.

You should have 31# of pressure on the rail.
 
Ok, I had some one else blow through the line that goes from the fuel filter to the rail. I checked the check valve on the rail, and, fuel came out. Once we reassembled the system, and ran the pump and then cranked the motor over. It still would not start, and when pushed in, no fuel came out of the rail. I'm now thinking that its certain that I have a weak pump, that can't pump the fuel up to the fuel rail. That pressure regulator could be somthing to look into, but the check valve is before the pressure regulator, and the check valve showes no pressure in the rail.

Another thing, does any one know where the relay for the fuel pump is. So far we haven't been able to find it. Thanks for the help you guys are giving me.
 
Do you hear the pump charging the system when you turn the ign key on??? You should hear it humm, then stop a few seconds later.

You are going to have to measure the pressure at the fuel rail. Even if the pump is running and pumping fuel, if you dont have enough pressure it's not going to run, or run very poorly. I've had that problem.

Is the vehicle level????

Take off the vacuum hose to the fuel pressure regulator in front of the fuel rail and turn the engine over....put your finger over the open end of the hose, see if you are getting any vacuum.

The ignition relay serves all power to the vehicle, one of those wires is probably for the fuel pump but your pump is working so I wouldnt bother with that.

There is a screen on the fuel pick-up inside the tank. Its possible its plugged up or another problem with the pickup. Thats happened to me, too.
 
Yeah, this does seem pretty hard to diagnose. The pump is running, and from testing it last night, I know that it is pumping fuel out of the tank. Also from the tests I did last night, I know that the lines are 100% clear from the tank to the fuel rail. The kicker is, eventhough I know the pump is running and pumping, and the lines are clear, there is no pressure in the Fuel rail, and the Test Valve is dry every time. This will also complicate trying to take a pressure test, since there is no pressure in the rail. I guess I could try hooking the guage up to the line that comes right off the gas tank. As I mentioned before, the pump is pumping kind of slow, but I think that's because I put a bigger hose on so that I get the gas to come out in a bucket and not all over the floor. The Jeep is level now, since I coasted it back into the garage. The Problem did start on a hill though. I parked it on the hill (which is kind of steep) and left it for maybe 2 hours to clean up the garage, and it would not start when I came back. Like I mentioned last night, its either a weak pump, or some how, the injectors won't fire, but that wouldn't explain why there is no pressure in the fuel rail.
 
the_bandit87 said:
Yeah, this does seem pretty hard to diagnose. The pump is running, and from testing it last night, I know that it is pumping fuel out of the tank. Also from the tests I did last night, I know that the lines are 100% clear from the tank to the fuel rail. The kicker is, eventhough I know the pump is running and pumping, and the lines are clear, there is no pressure in the Fuel rail, and the Test Valve is dry every time. This will also complicate trying to take a pressure test, since there is no pressure in the rail. I guess I could try hooking the guage up to the line that comes right off the gas tank. As I mentioned before, the pump is pumping kind of slow, but I think that's because I put a bigger hose on so that I get the gas to come out in a bucket and not all over the floor. The Jeep is level now, since I coasted it back into the garage. The Problem did start on a hill though. I parked it on the hill (which is kind of steep) and left it for maybe 2 hours to clean up the garage, and it would not start when I came back. Like I mentioned last night, its either a weak pump, or some how, the injectors won't fire, but that wouldn't explain why there is no pressure in the fuel rail.
Click to expand...

I would say you need to put a pressure gauge right on the pump, it can be pumping without pressure, your fuel will siphon from the hose without pressure. It will be about 75# hooked straight to your test gauge without going through thr rail..
 
What you describe is a bad fuel pressure regulator. If it is not holding back the fuel and thereby causing the pressure to rise, all that will happen is that the fuel circulates back to the tank. A quick check is to pull the return line and feed it into a bucket. If you get fuel of any significant quantity, the pressure regulator is the culprit. This is a fairly common failure.
 
I pulled the return fuel line and the pressure regulator appears to be closed, NO fuel comes out of it. From what I can tell, its still looking like a weak pump. I'm positive that no fuel is making it to the rail. I think the next think I'm going to try is taking off the fuel line at the intake manifold and see if any gas comes out there. I have a new Fuel Pump on order from Chrysler, only $100, so I think I did pretty good. This weekend, a friend of mine who is a mechanic is going to take a look at it. I guess its just a coincidence that it broke down while I parked it on a steep hill. Thanks again for the help, I'll let you guys know what happens next.
 
If you hear the pump running, you could have the simple problem that the short rubber hose that connects the fuel pump to the mount, could be bad or have come off. Led had this happen on the way back from Moab a couple of years ago. You can pull it and look before you pop for the $100.
 
the_bandit87 said:
I pulled the return fuel line and the pressure regulator appears to be closed, NO fuel comes out of it. From what I can tell, its still looking like a weak pump. I'm positive that no fuel is making it to the rail. I think the next think I'm going to try is taking off the fuel line at the intake manifold and see if any gas comes out there. I have a new Fuel Pump on order from Chrysler, only $100, so I think I did pretty good. This weekend, a friend of mine who is a mechanic is going to take a look at it. I guess its just a coincidence that it broke down while I parked it on a steep hill. Thanks again for the help, I'll let you guys know what happens next.
Click to expand...
Most of the time that pumps in stock at Autozone for about half that amount.
 
I'll have to check that short rubber hose. Are you talking about one inside the tank? I'm not sure though because I know that gas is getting out of the tank. That hose could explain why the pressure is so low. I'm going to try to get the seinding unit out of the tank tomorow to check out how bad my tank is inside, so I'll deffinatly check that hose.
 
Well, yestarday my friend dropped by, and later on his dad, who runs a garage and tow company, took a run by too. After looking at the jeep, cycling the pump, and turning it over, they both agreed that its probably that rubber hose in the tank. Because the pump is still working a little, its probably not a bad pump after all, its probably lost flow because that hose is broke. Tomorow I'm going to buy a florecent shop light, so I can check what the inside of the tank looks like. If that hose is gone, I'll just replace it and hold off on a new pump. What signs of aging, besides rust, should I look for inside the tank? My tank has a skid plate over it, and it hasn't had more than 3/4 of a tank in it durring the 6 years its been off the road. Most of the time it was under half, and from what I've heard this is when you get condensation forming inside the gastank and starting to rust it from the inside out.
 
The way it looks now is that I have to hope its just the hose. The Computers were down the day I ordered my new Fuel pump from Chrysler, and it turns out that they sent me a mechanical one. The other bad news is that the electric one is way more expensive. I could always spring for an aftermarket as long as its a good name (carter ect.) but my friend the mechanic and his father, who's probably the best trouble shooter around here ( sometimes he fixes brand new cars the dealerships can't) have me convinced that its probably that hose. Is there any way to test the pump for flow once its removed from the tank? I heard put it in a bucket of water, but I dunno. The other thing is, what are the specs on the rubber hose in the tank, basically I want to know what it is made of so I can get one made out of the right material so it won't swell, crack, ect. when exposed to gasoline. I've also been toying with the idea of installing a plastic drag racing fuel cell if my tank is bad. This is primarily for cost reasons only, but I was thinking it could be marginally safer (arn't they supposed to have mesh inside them) and I am also thinking about the cost (a bit cheaper than a new steel 20 gallon tank).
 
the_bandit87 said:
The way it looks now is that I have to hope its just the hose. The Computers were down the day I ordered my new Fuel pump from Chrysler, and it turns out that they sent me a mechanical one. The other bad news is that the electric one is way more expensive. I could always spring for an aftermarket as long as its a good name (carter ect.) but my friend the mechanic and his father, who's probably the best trouble shooter around here ( sometimes he fixes brand new cars the dealerships can't) have me convinced that its probably that hose. Is there any way to test the pump for flow once its removed from the tank? I heard put it in a bucket of water, but I dunno. The other thing is, what are the specs on the rubber hose in the tank, basically I want to know what it is made of so I can get one made out of the right material so it won't swell, crack, ect. when exposed to gasoline. I've also been toying with the idea of installing a plastic drag racing fuel cell if my tank is bad. This is primarily for cost reasons only, but I was thinking it could be marginally safer (arn't they supposed to have mesh inside them) and I am also thinking about the cost (a bit cheaper than a new steel 20 gallon tank).
Click to expand...
You just need fuel host that's labeled for fuel injection, most of the time though it's not the hose.
Autozone has/can get the OEM pump I mine had a Bosch and they ordered it for me overnight.
I tryed the store brand GLD or something and it would not fit the tank bracket, so it took it back and ordered the Bosh which was OEM $128.00.
 
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