Automotive Forums .com - the leading automotive community online! Automotive Forums .com - the leading automotive community online!
Automotive Forums .com - the leading automotive community online! 
-
Latest | 0 Rplys
Go Back   Automotive Forums .com Car Chat > Jeep > Wrangler
Reply Show Printable Version Show Printable Version | Email this Page Email this Page | Subscription Subscribe to this Thread
 
Thread Tools
Old 12-23-2017, 11:44 AM   #1
ASJT3
AF Regular
 
Join Date: Jan 2005
Location: Potomac, Maryland
Posts: 245
Thanks: 1
Thanked 6 Times in 6 Posts
Send a message via AIM to ASJT3
1991 Wrangler 2.5 no start

What tells the fuel pump relay to shut off? I’ve got a YJ no start, fuel pressure does not build. The relay will click over on key on, and will the energize after two seconds, as if it’s expecting the fuel pressure is already high and it’s just topping it off a bit. Is there a sensor that measures fuel pressure and tells the relay to shut off? Or could this be a problem with the pressure regulator? I didn’t put a gauge on the rail because it’s at my other house 40 mins away and I can tell the pressure is literally zero, no fuel even squirts out schraeder valve.

Thanks much,

Alex
__________________
2008 Tahoe SSV, 2007 Tahoe SSV, 94 GMC K1500, 93 Chev K1500, 91 GMC K1500, 2000 Wrangler Sport
ASJT3 is offline   Reply With Quote
Old 12-23-2017, 03:08 PM   #2
ASJT3
AF Regular
Thread starter
 
Join Date: Jan 2005
Location: Potomac, Maryland
Posts: 245
Thanks: 1
Thanked 6 Times in 6 Posts
Send a message via AIM to ASJT3
Re: 1991 Wrangler 2.5 no start

Worried I may be chasing my tail on this. There is good spark from the coil but weak spark from the cap. Dist cap and rotor replaced when I noticed this. Still not fixed. Could be bad pickup coil?
__________________
2008 Tahoe SSV, 2007 Tahoe SSV, 94 GMC K1500, 93 Chev K1500, 91 GMC K1500, 2000 Wrangler Sport
ASJT3 is offline   Reply With Quote
Old 12-23-2017, 06:08 PM   #3
harleyguy
AF Regular
 
Join Date: Apr 2016
Location: McPherson
Posts: 125
Thanks: 0
Thanked 10 Times in 10 Posts
Re: 1991 Wrangler 2.5 no start

If you have no fuel psi that needs addressed. Try spraying starter fluid in the intake see if it will run on that. If yes jump the relay to power the fuel pump.
harleyguy is offline   Reply With Quote
Old 12-24-2017, 04:56 PM   #4
ASJT3
AF Regular
Thread starter
 
Join Date: Jan 2005
Location: Potomac, Maryland
Posts: 245
Thanks: 1
Thanked 6 Times in 6 Posts
Send a message via AIM to ASJT3
Re: 1991 Wrangler 2.5 no start

Quote:
Originally Posted by harleyguy View Post
If you have no fuel psi that needs addressed. Try spraying starter fluid in the intake see if it will run on that. If yes jump the relay to power the fuel pump.

Thanks for info. Had already tried jumping the pump relay, still will not start. This morning, however, I hooked up a fuel pressure tester. While cranking pressure builds up to around 40 psi, but once cranking is done, it drops precipitously to zero.

Thinking it was a problem with the fuel rail-mounted pressure regulator, I clamped off the return line, expecting pressure to maintain. To my surprise, pressure dropped just as fast. Incidentally, i thought this was especially strange given that when I previously directed the return line to a container, fuel came flowing out when I jumpered the fuel pump relay.

Ruling out other possibilities, i really don’t think the injectors are that leaky. I took them off to test and at most a drip or two *may* have escaped one or two of them. This rapid fuel pressure drop has me at a loss. Is there supposed to be a check valve in the fuel pump that prevents this?

Spraying some starter fluid in it can get it to start occasionally, but it dies a split second later.

Thanks,

Alex
__________________
2008 Tahoe SSV, 2007 Tahoe SSV, 94 GMC K1500, 93 Chev K1500, 91 GMC K1500, 2000 Wrangler Sport
ASJT3 is offline   Reply With Quote
Old 12-30-2017, 01:01 PM   #5
rhandwor
AF Enthusiast
 
Join Date: Sep 2006
Location: Athens, Georgia
Posts: 4,662
Thanks: 0
Thanked 64 Times in 64 Posts
Re: 1991 Wrangler 2.5 no start

Quote:
Originally Posted by ASJT3 View Post
Thanks for info. Had already tried jumping the pump relay, still will not start. This morning, however, I hooked up a fuel pressure tester. While cranking pressure builds up to around 40 psi, but once cranking is done, it drops precipitously to zero.

Thinking it was a problem with the fuel rail-mounted pressure regulator, I clamped off the return line, expecting pressure to maintain. To my surprise, pressure dropped just as fast. Incidentally, i thought this was especially strange given that when I previously directed the return line to a container, fuel came flowing out when I jumpered the fuel pump relay.

Ruling out other possibilities, i really don’t think the injectors are that leaky. I took them off to test and at most a drip or two *may* have escaped one or two of them. This rapid fuel pressure drop has me at a loss. Is there supposed to be a check valve in the fuel pump that prevents this?

Spraying some starter fluid in it can get it to start occasionally, but it dies a split second later.

Thanks,

Alex
There is a check in the fuel pump. Check the fuel pimp ground it should be around the frame with a wire coming from the top of the tank to where it is bolted on. If loose it will shut down the engine. Check the ground for the ECM if loose it will shut you down. I would use a 12 volt test light and with the vehicle on a jack stand Unplug the wire feeding the pump. Check if the voltage to the pump is shutting off.
rhandwor is offline   Reply With Quote
Old 12-30-2017, 02:16 PM   #6
ASJT3
AF Regular
Thread starter
 
Join Date: Jan 2005
Location: Potomac, Maryland
Posts: 245
Thanks: 1
Thanked 6 Times in 6 Posts
Send a message via AIM to ASJT3
Re: 1991 Wrangler 2.5 no start

Ok, been doing extensive troubleshooting over the last few days and am still somewhat stumped.

Here’s what I know:
1) spark was good from coil but weak to the spark plugs. Replaced the distributor + pickup coil and plug wires. Solved that problem. Timed the dist rotor to TDC on #1 cylinder, verified twice. Also, ignition coil and cps are new.

2) fuel pressure is good while cranking (I.e., steady at 40 psi) but drops off when key off - not sure if this is normal or not but with that good pressure at injectors while cranking should be good for a start.

3) compression is good (I.e., 120 psi) on all 4 cylinders.

4) Vacuum is bad. Flutters rapidly between 0-5 inHg while cranking. Starting to suspect that I may have a timing chain that has jumped a cog here, thoughts?
__________________
2008 Tahoe SSV, 2007 Tahoe SSV, 94 GMC K1500, 93 Chev K1500, 91 GMC K1500, 2000 Wrangler Sport
ASJT3 is offline   Reply With Quote
Old 12-31-2017, 10:26 AM   #7
rhandwor
AF Enthusiast
 
Join Date: Sep 2006
Location: Athens, Georgia
Posts: 4,662
Thanks: 0
Thanked 64 Times in 64 Posts
Re: 1991 Wrangler 2.5 no start

You can use WD-40 and spray along edges of intake manifold while cranking. If you find a leak replace the gasket.
Get a long 1/2 drive ratcket with a socket that fits on the bolt for the harmonic balancer. Turn 180 degrees then align the timing mark at 0 degrees. Pull the distributor cap use white out and mark the rotor tip. Assuming you turned clockwise now turn counter clockwise stop when the rotor starts to move anything over about 10 degrees will cause problems.
rhandwor is offline   Reply With Quote
Old 01-01-2018, 12:43 PM   #8
ASJT3
AF Regular
Thread starter
 
Join Date: Jan 2005
Location: Potomac, Maryland
Posts: 245
Thanks: 1
Thanked 6 Times in 6 Posts
Send a message via AIM to ASJT3
Re: 1991 Wrangler 2.5 no start

Quote:
Originally Posted by rhandwor View Post
You can use WD-40 and spray along edges of intake manifold while cranking. If you find a leak replace the gasket.
Get a long 1/2 drive ratcket with a socket that fits on the bolt for the harmonic balancer. Turn 180 degrees then align the timing mark at 0 degrees. Pull the distributor cap use white out and mark the rotor tip. Assuming you turned clockwise now turn counter clockwise stop when the rotor starts to move anything over about 10 degrees will cause problems.
Holy cow, nearly 16 degrees of lash prior to rotor movement! New timing chain then?
__________________
2008 Tahoe SSV, 2007 Tahoe SSV, 94 GMC K1500, 93 Chev K1500, 91 GMC K1500, 2000 Wrangler Sport
ASJT3 is offline   Reply With Quote
Old 01-03-2018, 08:28 PM   #9
ASJT3
AF Regular
Thread starter
 
Join Date: Jan 2005
Location: Potomac, Maryland
Posts: 245
Thanks: 1
Thanked 6 Times in 6 Posts
Send a message via AIM to ASJT3
Re: 1991 Wrangler 2.5 no start

Well...took off the timing cover and this is what I found: the camshaft sprocket was completely stripped (teeth were stumps); the chain tensioner was limp and no longer sprung; the chain guide was missing and guide supports were machined away (apparently by the chain); and the camshaft and crank sprockets were misaligned.

Rotating the crank by hand I clearly witnessed the chain slipping over the cam sprocket. Will replace the sprockets, chain, tensioner, and guide and also drop the oil pan to empty out the probable debris within.

I’ll report back with the outcome!

(Edit): I should clarify that The cam was not frozen. It still rotated (and I still get good compression) but The chain would slip every now and then. Could not the absence of the chain tensioner for an extended period eventually wear down the Cam teeth and cause this issue?

Also, this morning I pulled off the valve cover and rotated the cam by hand to witness valve operation and everything appeared normal
__________________
2008 Tahoe SSV, 2007 Tahoe SSV, 94 GMC K1500, 93 Chev K1500, 91 GMC K1500, 2000 Wrangler Sport

Last edited by ASJT3; 01-04-2018 at 06:33 AM.
ASJT3 is offline   Reply With Quote
Old 01-10-2018, 09:57 AM   #10
ASJT3
AF Regular
Thread starter
 
Join Date: Jan 2005
Location: Potomac, Maryland
Posts: 245
Thanks: 1
Thanked 6 Times in 6 Posts
Send a message via AIM to ASJT3
Re: 1991 Wrangler 2.5 no start

Replacement of the timing chain and sprockets solved the problem. Thank you to everyone for their help!

By the way, I did not end up replacing the fuel pump. Can anyone confirm that for these pre-1997 2.5L, the fuel pressure does not maintain in the rail after shutdown? As noted previously, It builds fine to 40 psi while cranking and running but then drops precipitously during following shutdown. My sense is that this is normal behavior since the rail-mounted fuel pressure regulator appears to be basically just a flow restrictor and not an actual valve.

Alex
__________________
2008 Tahoe SSV, 2007 Tahoe SSV, 94 GMC K1500, 93 Chev K1500, 91 GMC K1500, 2000 Wrangler Sport
ASJT3 is offline   Reply With Quote
Old 01-10-2018, 05:10 PM   #11
rhandwor
AF Enthusiast
 
Join Date: Sep 2006
Location: Athens, Georgia
Posts: 4,662
Thanks: 0
Thanked 64 Times in 64 Posts
Re: 1991 Wrangler 2.5 no start

Generally they are located in the fuel pump. Some have had the hose leak between the top of the fuel pump and the outlet. This is about 3 inches long use 100psi high pressure hose. O'Reilly sell Gates high pressure hose. I would purchase a new sock or filter for the fuel pump if trying this procedure.
rhandwor is offline   Reply With Quote
 
Reply

POST REPLY TO THIS THREAD

Go Back   Automotive Forums .com Car Chat > Jeep > Wrangler

Thread Tools

Posting Rules
You may not post new threads
You may not 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



All times are GMT -5. The time now is 12:36 PM.

Community Participation Guidelines | How to use your User Control Panel

Powered by: vBulletin | Copyright Jelsoft Enterprises Ltd.
 
 
no new posts