help with fuel pump diagnosis

[orange]

X2 birchlakeXJ 's thought.

- Need to do some FSM and metering.
----------------------------------------------------
-get a fuel pressure gauge and check pressure key on and then key off does it hold?
does pressure hold up while cranking.

-check a sparkplug dry then install try starting and pull plug and check condition?

 

[jeepnfreak]

Security maybe. had simular problem except mine would try to start, locking and unlocking the lift gate fixed it right up. But from what youve said so far thats probably not it. Either compression or timing from the sounds of it. Air, fuel, compression, and spark at the proper time it has to start. Still I would have to try the lock, unlock especially if the battery was removed or discharged.

 

[markg]

i checked the ohms at the crank sensor plug last nite and although i thought i found a problem when i checked the brand new one at autozone it measured exactly the same.the absolute last thin on the list of things i have not done yet is the cam sensor.autozone advance auto and napa all claim they have no listing for one for the 91 4.0.they do sell a pickup assembly that needs the dist to be taken apart to put in .is this the coil sensor?
its about 60 bux but a whole new dist is 85.i think im going to buy a new dist.the new dist says "without module" but clearly it has the internals and the wire coming out of it.
do you think this will do the trick?
i am at my witts end with this and its going to be the coldest weekend yet here?

does anyone know what the procedure is for checking the wires coming out of the dist?

 

[birchlakeXJ]

the absolute last thin on the list of things i have not done yet is the cam sensor.autozone advance auto and napa all claim they have no listing for one for the 91 4.0.they do sell a pickup assembly that needs the dist to be taken apart to put in .is this the coil sensor?its about 60 bux but a whole new dist is 85

I imagine that what they call the pickup assembly is the camshaft position sensor. Some parts stores still refer to this as either the "pickup coil" or the "stator".

I don't have the procedure for testing the camshaft position sensor but if you search here or on Jeep Forum, I would bet you'd find it pretty quickly, it's been posted a number of times.

 

[markg]

i found this and it is very informative.

http://www.lunghd.com/Tech_Articles/Engine/Cam_Position_Sensor_and_Sync_Pulse_Stator.htm

 

[orange]

Did a bit of digging and seems the chiltons etc. around that year have bad info on the distributor wires watch out! Best i can find is.. (NOT Positive this is for 1991 but believe it is)

standing on right side looking across engine to drivers side(12 o'clock), #1 cyl should plug in at 5 o'clock on the cap. Go Clockwise 153624 on cap. Also distributor can be mounted with rotor pointing wrong-check rotor is at 5 o'clock with cyl #1 TDC

old memory aid: 15 too young, 36 too old, 24 just right!

Good Luck,
Orange

 

[winterbeater]

Whoa! Take a step back for a minute. You put in new plugs and a coil and had a good spark. Did you try spray start again AFTER that? If it does work, you have a fuel problem.

On a different more ominous note, this could be like an old Fiero that my son had. It seemed to run fairly well until one cold morning when it would not start or even kick although it was cranking well. We had spark. It was a throttle body injection, so we could tell we had gas, and we also checked the spark plugs and tried spray start.

Combustion requires spark, fuel, and compression. Checked compression - it was only about 100psi. Did a poor man's hone and re-ring. Started immediately and ran well for a couple of years until he got rid of it.

Check your compression!

 

[orange]

X2 whoa!

This seems to have started as something 'broke' with C-C-Cold !!!. Need to Stop and get some data and tests done:

-Check that Battery is strong. And keep it so.

-Really, Really need to get a gauge on the fuel pressure- What is the PSI ?????:
-Key on first 3 seconds or so?
-Does it hold pressure after the 3 seconds?
-Pressure while starter turning engine over?
-Then -key off is pressure holding up?

-Pull a sparkplug and verify its DRY??? put a DRY one back in and try a start, pull the plug and verify if its wet or dry????
-Noid light injectors

There is a possible its flooded and needs several turns with ~1/4 throttle to clear.

This should show that the "fuel" is ok or point to a problem.

Basics:
Air-Fuel-Spark, in correct amounts and proper time it will run.

Air- Check
Fuel-?
Spark-?

 

[joe_peters]

Buy a NOID light, $3. Use the noid light to test for a signal at the injectors. If you are getting a signal, then the synch sensor in the distributor is working. It is a replaceable part, and they will go out, but much less common than the crank sensor. If you have spark then the crank sensor is working, as that is what the ECU/PCM uses to determine when to trigger the spark.

Check to see if you have power to the pump at the correct times.

Power to the pump when the key is turned to the ON position is through the ASD relay, bypassing the ballast resistor, providing 12v to the pump for 3 seconds, then the ECU/PCM will cut the signal to the ASD relay if it hasn't gotten a signal from the crank sensor.

Power to the pump when the key is in the START position is direct from the starter relay, bypassing the ballast resistor, providing a full 12v to the pump.

Engine running, from idle to just short of WOT, power to the pump is from the fuel pump relay through the ballast resistor which reduces the voltage to the pump for quieter operation.

At WOT, power is direct to the fuel pump from the oxygen heater relay, bypassing the ballast resistor, providing a full 12v to the pump.

Now, all that said, if you have flooded the engine while cranking it with 1) bad plugs; 2) low fuel pressure; and 3) low voltage from a discharged battery, and combine that with extremely low temperatures and fuel with ethanol (if required in NJ), you are set up for a hard time to get it restarted.

Fuel, air, spark, compression, all at the right time at the right places. I would charge that battery for a minimum of 24 hours, then take it in and have it load tested. Starters are dirt dumb and really don't care much about voltage as long as the amps are there. On the other hand, if the voltage drops too much while cranking, say near 9 volts or less, then the electronics are not going to work properly.

While the battery is out charging clean the cables--both ends, and while you have them disconnected test them with an ohm meter. Resistance should be near ZERO; if not, replace them. Good time to renew all of the grounds, firewall, dipstick tube, block.

While all of this is going on pull the plugs and let the engine air out.

Post back and let us know what you find.

 

[markg]

thanks for all the info!
sat we put in a new distributer.we cranked and for the 1st time it felt like it was firing a bit but only for a sec or 2 and would not start even for a few seconds.we did this a few times and then the batt started getting low so i put the charger on it.after about 15 min we tried cranking it but i still had the charger on it.turning the key did nothing at all.now we had a whole new problem.we tried for an hr or so to get it to crank but got nothing.freeeeezing by now and gave up.
next day started again.wouldnt crank in park or neutral.
called a friend who works on jeeps and he came over.he had a real fancy test lite and tested some of the wires at the ign switch on the column.things seemed ok there.went out to the power dist box and swapped a few relays.still nothing.looked at the wiring diagram and found that the neutral safety switch seemed to be the problem.we ran a wire from one of the terminals on the relay to the ground on the batt and at least now it would crank.
it seemed again like it wanted to go but just wouldnt.i held the throttle open and it started up finally!
he said that the problem was prolly the cam sensor in the dist and that if we didnt run into the no crank problem that we prolly would have gotten it to start on our own.
the problem now is that it is running very rough.it almost seems as if it has a bad miss.
i pulled #1 plug and watched for the piston to come up then looked where the rotor was pointing and it was 180 out but the timing mark was not lined up either.we cranked it around untill the timing mark lined up while i looked at the piston and it all looked right.tdc,rotor at #1 and the timing mark was lined up.
we started it up and pulled each wire off 1 by one but it ran worse as each was pulled so i think everything is working ok.
we have replaced everything but the cap wires and rotor(new within a yr ago)and the crank sensor(dont think this is a problem).
i bought a new cap and rotor tonite and will try it tomorrow.it a good one with brass terminals.
any ideas as to why it is running so rough now?
i pulled the ground off the batt for a while hoping the computer would reset but this didnt help.
it didnt run rough like this before we had the problem and its got many new parts that shoud make it run like a top now.

again thank you all for all of your help!

 

[dennis461]

any ideas as to why it is running so rough now?

Plug wires in wrong place, broke a spark plug, broke a wire.
Are you anywhere near Camden County, Atco?
I have a 1991...

I don't have a fancy test light, but I know how to jumper the relays.
Which fuel pump did you put in?
Did you replace the filter?
Did you crimp the stell lines by error?

 

[markg]

we put a new cap and rotor in tonite.an expensive one with brass terminals.started fine but still runs kinda rough.my son took it out for a ride and i drove behind him in case there was a problem.it went well but i could smell a horrible burning smell that is hard to describe.there is no smoke at all but the smell is very strong and it is coming from the exhaust.the tailpipe broke off a while ago but the factory cat is in place and a magna flo muffler.i never tested this before but the exhaust is coming out so hot that i cant keep my hand in front of it for more than a second or two.
could this be related to the other problems im having?

 

[crofoot]

Sounds like cat is starting to clog,raw fuel will start to melt interals.Try unbolting the cat and see if it runs better.The smell is a good indicator of this problem.

 

[cliff h]

A plugged cat could do something similar to your problem. I dont often think of a bad cat. converter myself, but I have seen a plugged cat do some strange things. I suppose you could disconnect the exhaust by the manifold for testing purposes. Post up if you fix this, what a saga this has been. It would be nice to know what finally fixes your problem.

 

[dshaff24]

After reading this post I feel like I still got hope! My 91 xj is doing everything this post decribes to a T and can't wait to go to work and swap out the cam sensor!

As far as the smell its def the cat, It probally is full of tons of raw fuel from all that cranking! One thing I noticed from the past is cats will cause a loss in power and once they get to bad your rpm's will cut out

Anyway Thanks Mark for this post! I hope to chime back in with the same success story because I WENT THROUGH everything you did Just not in the cold!