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1987 XJ running problem

alfman

NAXJA Forum User
NAXJA Member
Location
Pike Co, PA
I am having a start and run problem. I started it and moved it to work on the body and it ran fine. Went to start it 6 hours later and it won't run. It was flooding out. Pulled out the fuel pump relay, let it sit for 2 days and it starts right up until it runs out of fuel pressure. Put the relay back in and it coughs a couple of times and won't stay running. Pull the relay and 2 days later it starts. Would this possibly be the fuel pressure regulator at the front of the fuel rail? Any other ideas? I really don't want to just buy parts and throw them at it.
 
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When you think it is flooding, pull the vacuum hose off the Fuel Pressure Regulator mounted on the fuel rail. If there is fuel on the vacuum side of the FPR, you have a problem there.
 
It would not hurt to replace the inexpensive fuel pump relay. With time the contact points, inside the relay, get corroded and dirty and start malfunctioning, These mechanical-electric relays are typically not sealed well.

Best regards,

CJR
 
CJR, relay has been changed as I thought it was a no fuel problem, it actually floods out. Let it sit for a day without the relay in and it starts with the residual fuel pressure. Put the relay back in and try to start and it sputters and it floods out.

Cruiser54, I have been on the site. Map sensor line has been checked and isn't leaking. Sort of why I was thinking it was the regulator not working.

Hypoid, I had pulled the vacuum hose off and it was dry.
 
You might want to check-out your Throttle Position Sensor (TPS). TPS are like fuel accelerator pumps on carburetors. The TPS tells the computer what the throttle position is with a voltage. The computer then controls how long the fuel injector stays open. If the TPS is defective and gives a low voltage to the computer, the computer thinks the engine needs more fuel and keeps the fuel injectors open longer and floods the engine. If it happens during start-up(open loop), the computer is typically not looking at the oxygen (02)sensor. It is my understanding that the computer looks at the 02 sensor once the engine warms-up and the computer goes into "closed-loop".

Best regards,

CJR
 
CJR, I'll give that a try, sort of makes sense.
 
The couple of times I had a flooding problem in my 87 it was either the IAC or weak spark.
If the IAC sticks shut you have to give 1/8 pedal so you get a little air while cranking. Pumping the pedal seldom helps. One trick is to hold the pedal all the way down and crank it over for half a dozen seconds, WOT during cranking helps purge the excess fuel out of the cylinders. Then try 1/8th pedal. Or a squirt of quick start down the TB.

Weak spark is easy to test and fairly common for various reasons. Low voltage through the (thicker) yellow wire to the ignition module or maybe the connector between the module and the coil is corroded, rotted or just loose. Spark plug/coil wires can have high resistance of even moisture in the boots. The distributor cap can be excessively worn/burnt poles.

One thing that drove me nuts on one occasion was a little moisture inside the distributor. It would sometimes start cold and then run really bad when warm.

It may have nothing to do with fuel the CPS can be iffy, sometimes it works sometimes it doesn't. Could be corrosion in the CPS connector. Could be a weak CPS signal. Could be the temperature, as the CPS can be temperature sensitive. Could be an oil-soaked CPS.
 
does your year have the fuel pump ballast ?
Cos I think it does.
If it does.
Take it out. Smash it to smithereens with a hammer. and solder those wires together.
 
Beyond that. Mine is a 92 and my fuel pump grounds crapped out in me last year (inside the tank) and passenger side of the engine by the dipstick.
Clean those grounds.
 
Blu3fan, I have a problem with too much fuel. Grounds were cleaned twice. Fuel pump and sender were replaced last year due to the bulkhead where it's held in the tank rotted out around the fuel lines. Spark was checked and it will run on residual fuel pressure after sitting for a day with the fuel pump relay pulled. As soon as it stops raining and I get a chance I am going to clean the throttle body and check out the TPS.
 
Here's my followup, Cruiser54, thanks. Traced the ground from TPS back to the crimp of 3 brown with white wires to 1 wire that goes to the bulkhead connector. Connection was clean but intermittent loss of ground. I soldered the connection and re-taped it. The only other connection I found like that was the 6 wires into 1 which traced back to the injector grounds. That crimp was already soldered. Started right up.
 
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Here's my followup, Cruiser54, thanks. Traced the ground from TPS back to the crimp of 3 brown with white wires to 1 wire that goes to the bulkhead connector. Connection was clean but intermittent loss of ground. I soldered the connection and re-taped it. The only other connection I found like that was the 6 wires into 1 which traced back to the injector grounds. That crimp was already soldered. Started right up.

Gotta love it!!!!! You made my day.
 
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