Jeep running without fuel pump relay? - JeepForum.com
 1Likes
Reply
 
LinkBack Thread Tools
post #1 of 24 Old 06-17-2019, 05:53 PM Thread Starter
PaulFromCalif
Registered User
1998 TJ Wrangler 
 
Join Date: Oct 2016
Location: Riverside
Posts: 41
Jeep running without fuel pump relay?

97 TJ 2.5 4cyl sat for a long time. Ran good last time I ran it. Battery was dead, charged it, cranked and started but ran bad and only for a few seconds. After that it wouldn't start. Smelled fuel which smelled bad, varnish. Figured fuel might be bad. It only had a 1/4 tank. I added 2 gallons of fresh fuel. Still wouldnt start. Tried starting fluid, still cranked good but wouldnt start. Pulled a plug and tested for spark, sparked good. Pulled the plastic intake from the fuel body intake (in my day that would have been the carb, not sure if that's the right name. The bottom was full of fuel. I soaked it up with paper towels, shot it with starting fluid, cranked it, and it started briefly. Fuel body was flooded again. I pulled the fuse for the fuel pump, hit it with starting fluid again, and it started. Gave it occasional starting fluid blasts to keep it running. Ran over and put the fuel relay in and it almost died. Thought maybe the relay was locked closed. Switched it with horn relay, same thing. It's idling now and has been for several minutes, I can even rev it and it keeps running. WTF, put the relay in, 10 seconds later it almost dies, take it out, it runs, not great, but it runs. Could it be pulling a vacuum through the injectors? Could the gas be bad and the correct amount of Bad fuel be fouling it. What do you guys think? How long can it idle on 1/3 tank? Should I fill it with fresh fuel or idle it until the fuel in it is gone? I tried to put a syphon hose in the gas fill, but it stops after a couple feet. Need some advice here. Exhaust stinks

PaulFromCalif is offline  
Sponsored Links
Advertisement
 
post #2 of 24 Old 06-17-2019, 08:55 PM Thread Starter
PaulFromCalif
Registered User
1998 TJ Wrangler 
 
Join Date: Oct 2016
Location: Riverside
Posts: 41
Jeeps been running without fuel pump relay at idle now for over 2 hours. Burning up the bad fuel. Weird...
PaulFromCalif is offline  
post #3 of 24 Old 06-17-2019, 11:13 PM
mukluk
Web Wheeler
 
mukluk's Avatar
2000 TJ Wrangler 
 
Join Date: Oct 2010
Location: Clyde
Posts: 5,123
The Jeep is highly unlikely to run unless the pump is actually operating since the fuel injection requires a fair bit of pressure to get the fuel to atomise... it's not like a carbureted engine that can still operate via gravity flow from the tank if the pump goes kaput.

If the Jeep operated normally with the pump relay installed prior to sitting for an extended period and none of the wiring was messed with, there's definitely something screwy going on here. Do you have any aftermarket electrical equipment installed on the Jeep? Just to verify, does your PDC and relay layout match the diagram attached below? Checking first with the relay installed and then with it removed, when you first turn the ignition switch to run (not start) do you hear the fuel pump kick on for two seconds then shut off?
Attached Images
 

2000 TJ SE
2005 LJ Rubicon
mukluk is offline  
 
post #4 of 24 Old 06-18-2019, 10:23 AM Thread Starter
PaulFromCalif
Registered User
1998 TJ Wrangler 
 
Join Date: Oct 2016
Location: Riverside
Posts: 41
There was an after market storeo installed in the Jeep before I purchased it, with a amplifier. It's long gone but the wire that was going to it is disconnected and under the hood. There is also a small volume control for something under the dash that I assume was part of the stereo, it doesnt seem to do anything. A couple of years ago the ecm went out. I replaced it with one that was programmed to my VIN#. It has work fine until now. Unfortunately, your attachment was blocked, but I believe everything else on the Jeep is stock. I let it idle last night until it ran out of fuel, now its empty. I was thinking that maybe an injector is stuck open and allowing vacuum to pull in fuel?? That might explain why there was so much fuel in the throttle body. I'll go out and listen for the fuel pump, fuse in and out and report back.
PaulFromCalif is offline  
post #5 of 24 Old 06-18-2019, 11:26 AM Thread Starter
PaulFromCalif
Registered User
1998 TJ Wrangler 
 
Join Date: Oct 2016
Location: Riverside
Posts: 41
Your diagram came through on my computer, just not on my phone. It appears to be the same as my Jeep's. Removing the relay and turning the key on, no fuel pump sound. Putting the relay in, turning on key, fuel pump makes noise. ALSO, I heard a fluid rushing sound under the hood. Eureka moment. Pulled the air intake off of the throttle body again, there was a little fuel sitting in the bottom of it. I took a hand vacuum pump and sucked out the fuel. Then I turned the key on and off several times with the fuel pump relay in, cycling the fuel pump. Kept hearing the sloshing, fluid noise from under the hood. Checked the bottom of the throttle body, and it had a LOT of fuel sitting in the bottom again where I had just removed it. The ONLY way I can think of for that fuel to go from the fuel rail into the throttle body would be through an injector. I would assume that the injectors should be closed until the engine is turning over, but I was not turning it over, just turning the key to on. Now I am guessing that my theory may be correct. Stuck open injector allows cylinder vacuum to pull fuel into fuel rail and allows the engine to run without a fuel pump!! Anyone see any other possibilities??
PaulFromCalif is offline  
post #6 of 24 Old 06-18-2019, 11:39 AM
Rubi4MyMrs
Web Wheeler
 
Rubi4MyMrs's Avatar
2005 LJ Wrangler 
 
Join Date: Mar 2011
Location: Trails of
Posts: 4,088
To be clear, are you seeing gas above the throttle plate (butterfly) in the throttle body?
Rubi4MyMrs is offline  
post #7 of 24 Old 06-18-2019, 11:46 AM
Rubi4MyMrs
Web Wheeler
 
Rubi4MyMrs's Avatar
2005 LJ Wrangler 
 
Join Date: Mar 2011
Location: Trails of
Posts: 4,088

You added the last post as I was typing so appears it appears the gas is in the manifold, not above the TB.

If so, I would guess the engine could run if manifold vacuum is pulling fuel in from a vapor hose from the tank. If that happened to be the case, adding fuel through the injectors when the fuel pump is running would (could) flood & kill the engine.

A stuck injector would not be getting fuel through it without the fuel pump pushing fuel to it (under pressure) as mukluk pointed out.
Rubi4MyMrs is offline  
post #8 of 24 Old 06-18-2019, 12:42 PM Thread Starter
PaulFromCalif
Registered User
1998 TJ Wrangler 
 
Join Date: Oct 2016
Location: Riverside
Posts: 41
Thanks for all of the replies. I just typed up a long reply but my login timed out, argh.
You are correct, it is the base of the intake manifold that has fuel, not the throttle body.
The bottom of the intake has a ridge that separates the intake just at the bottom so that when it fills with fuel, I can see whether the fuel is coming from the front of the manifold or the rear. I vacuumed out all of the fuel, then cycled the fuel pump 10 times, engine NOT running, and the front portion of the manifold filled with fuel. So, the fuel pump is pumping fuel into the manifold and I can only assume it's through a stuck open injector. I disconnected the wires to all of the injectors, repeated the test and got the same results. This tells me that, at least in this test, that vacuum is not pulling the fuel in. It would be coincidental if the vacuum was pulling fuel into the manifold through the return line AND the fuel pump was putting gas into the manifold. Still think it's not a stuck injector??
PaulFromCalif is offline  
post #9 of 24 Old 06-18-2019, 01:24 PM
underscore
Registered User
2007 WK 
 
Join Date: Dec 2016
Location: Kelowna
Posts: 1,815
It kind of sounds like somebody hooked the fuel return line to the intake manifold (so the vacuum can suck fuel vapour from the top of the tank) and either capped off the return line or hooked it to the intake as well. I'd leave the relay in and turn the key on (not running) or jump power to the pump with the intake apart and see where exactly fuel is coming in from.

07 WK CRD//QDII//OME MD//OMG WTF BBQ [daily]
91 Celica GTFour RC [for sale]
underscore is offline  
post #10 of 24 Old 06-18-2019, 01:30 PM Thread Starter
PaulFromCalif
Registered User
1998 TJ Wrangler 
 
Join Date: Oct 2016
Location: Riverside
Posts: 41
Well heck, eating crow here. I have the injectors out, but still attached to the fuel rail. Turned the key on once and expected to see where fuel sprayed out of one on the injectors, but nothing. I believe the intake is STILL filling up with fuel, so now I'm stumped. Got a phone call that pulled me away, but will go back to see where the fuel line connects to the manifold. I think there may be a leak underneath the manifold as things look wet under there. I can only assume now that the return line is connected to the manifold somewhere.
PaulFromCalif is offline  
post #11 of 24 Old 06-18-2019, 01:30 PM
Rubi4MyMrs
Web Wheeler
 
Rubi4MyMrs's Avatar
2005 LJ Wrangler 
 
Join Date: Mar 2011
Location: Trails of
Posts: 4,088
OK. Good testing.


That does sound like a stuck injector but the real question then becomes when is the fuel pump actually running? Is it running in your test? More importantly is it running when the relay is out? If the manifold only fills when the key is on are you sure the pump is not running? It is possible the key is actuating the pump without going through the relay? Possible if the wiring has been “modified” possibly by a previous owner. Without a stuck injector it would run normally & could be undetected. Just looking at all of the possibilities we can think of…
Rubi4MyMrs is offline  
post #12 of 24 Old 06-18-2019, 01:36 PM
Rubi4MyMrs
Web Wheeler
 
Rubi4MyMrs's Avatar
2005 LJ Wrangler 
 
Join Date: Mar 2011
Location: Trails of
Posts: 4,088
You are ahead of me again. There is no return line that I know of. For sure not on the 4.0 & even then unless the pump is running there should be nothing getting to the engine (that way).

If the pump is working as it should & not with the relay pulled but still filling the manifold when the key is on I would pull all of the vacuum hoses from the manifold & turn the key on & see what happens.
Rubi4MyMrs is offline  
post #13 of 24 Old 06-18-2019, 02:01 PM Thread Starter
PaulFromCalif
Registered User
1998 TJ Wrangler 
 
Join Date: Oct 2016
Location: Riverside
Posts: 41
I found it. The fuel pump DOES work, maybe I wasn't clear about that, and it only works when the relay is in. The problem is a ruptured diaphragm in the fuel pressure regulator that has a vacuum connection connected to the under side of the intake manifold. There is no return line as you guys stated so the only other way fuel could get into the manifold was through that vacuum line. You nailed it, even though I figured it out before I read your post . Now to go get one of those and put it back together. Thanks everyone, I'll report back once finished
PaulFromCalif is offline  
post #14 of 24 Old 06-18-2019, 02:44 PM
underscore
Registered User
2007 WK 
 
Join Date: Dec 2016
Location: Kelowna
Posts: 1,815
On the plus side you now know how to get it to run even if the injectors or fuel pump fail.

07 WK CRD//QDII//OME MD//OMG WTF BBQ [daily]
91 Celica GTFour RC [for sale]
underscore is offline  
post #15 of 24 Old 06-18-2019, 02:47 PM
Rubi4MyMrs
Web Wheeler
 
Rubi4MyMrs's Avatar
2005 LJ Wrangler 
 
Join Date: Mar 2011
Location: Trails of
Posts: 4,088
Good work!

I forgot that had vacuum to it.

In case you have trouble finding a replacement it is not a regulator & I forget the actual name but something like a fuel rail buffer. I think it is to reduce pressure spikes & only used on 4 cylinder engines.
Rubi4MyMrs is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.



Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome