Fuel pump issues, maybe? (FIXED!!)

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csuengr
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Joined: Sun Mar 24, 2013 10:24 am
Location: Sterling, CO

Fuel pump issues, maybe? (FIXED!!)

Post by csuengr »

My Cherk started to stumble last Sunday and it was worse last night. So I put Ye Old pressure gauge on it and it reads a steady 44 psi at idle. However, when I gas it, the pressure drops towards 35 psi. I tried the CJ, and the gauge stays at 44 psi. Doesn't even wiggle when I gas it. Is this a pump issue? Maybe filter (has 10k miles on it)? I really, REALLY don't want to drop the tank. Plus there is probably 25 gallons of gas in it.
Last edited by csuengr on Sat May 30, 2015 12:02 pm, edited 1 time in total.
1977 Cherokee S, Ford 5.0, 5 speed, BW 1356, 33 x 10.50 BFG's. No longer my DD.
2007 Mercury Milan, 2.3L, 5-speed, now my DD. 29 mpg average.

Topic author
csuengr
Posts: 1290
Joined: Sun Mar 24, 2013 10:24 am
Location: Sterling, CO

Re: Fuel pump issues, maybe?

Post by csuengr »

OK, so after new fuel pump and fuel filter and now gave steady fuel pressure, but still have missing and backfiring through the throttle body. Oh crap.
1977 Cherokee S, Ford 5.0, 5 speed, BW 1356, 33 x 10.50 BFG's. No longer my DD.
2007 Mercury Milan, 2.3L, 5-speed, now my DD. 29 mpg average.
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Lumpskie
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Location: New Hampshire

Re: Fuel pump issues, maybe?

Post by Lumpskie »

Clogged fuel filter somewhere? (maybe a previous owner installed one where you wouldn't expect?)
1989 Grand Wagoneer - Rebuilt 360, 2" Alcans, 10" travel Gabriel Guadian shocks.
1996 Land Cruiser - 1HD-T Diesel, Gturbo (23psi), Wholesale Automatics 442f, F/R ARBs, 35" Duratracs, ARB Rear Bumper, OME 2" lift, home built sliders and aluminum belly skid
2000 Honda Civic - Integra GSR engine, transmission, shift linkage and axles, 200hp, 33 combined mpg
2006 Mitsubishi Lancer Evolution 9 - 437hp/447ft-lb

Topic author
csuengr
Posts: 1290
Joined: Sun Mar 24, 2013 10:24 am
Location: Sterling, CO

Re: Fuel pump issues, maybe?

Post by csuengr »

I know where everything is 'cause I put it there. My fuel system is not in anyway stock. (5.0 Exploder engine) So today I am going to clean the MAF and check for vacuum leaks since the whole problem is caused by a severe lean condition. Too much air or not enough fuel. If that doesn't work, then I am pulling the injectors and cleaning them. We have an injector cleaning/balancing machine at work.
1977 Cherokee S, Ford 5.0, 5 speed, BW 1356, 33 x 10.50 BFG's. No longer my DD.
2007 Mercury Milan, 2.3L, 5-speed, now my DD. 29 mpg average.

Topic author
csuengr
Posts: 1290
Joined: Sun Mar 24, 2013 10:24 am
Location: Sterling, CO

Re: Fuel pump issues, maybe? (FIXED!!)

Post by csuengr »

Here is what I have done.

New coil packs.
Pulled all vacuum hoses off manifold, plugged ports.
Put in spare ECU.
Sprayed carb cleaner around upper intake and lower, no idle change.
New fuel pump and filter. Old pump would drop to ~35 psi when engine was revved. Fuel pressure is now rock steady.
Injectors were pulled and flow tested. All were with 1.5 mL of each other.
Sprayed water (while dark out) around (old) coil packs and ignition wires and there were no sparks
Pulled spark plugs. All LOOKED perfect.
Cleaned MAF.
Graphed both pre-cat O2 sensors and they tracked virtually the same and the graphs look normal.

None of the above had any affect on the way it runs. One interesting note, I pulled the plug wire off the coil pack for #1 cylinder and was rewarded with two codes. P0171 and P0174. Bank one too lean and bank two too lean. I duno.

Well, I eventually found the problem. It was a bad spark plug or two or so. New plugs, no problem. Now I have an issue as why the ECU wasn't detecting a missfire.
1977 Cherokee S, Ford 5.0, 5 speed, BW 1356, 33 x 10.50 BFG's. No longer my DD.
2007 Mercury Milan, 2.3L, 5-speed, now my DD. 29 mpg average.
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