1992 MGM won't start

[MacGyver-it]

A few months ago I took the old girl out for a short delivery errand returned home and parked her as usual. A couple days later I got in, turned the key and although she turned over she refused to start. I had run the gas pretty close to vapor so got 5 gallons of fresh fuel into the tank and tried again.. No still no start. Check for spark.. Looks good. Checked the e-shut off valve in the trunk, no problem there it hadn't tripped. Disconnected the fuel line from the tank to the fuel filter and placed it in a cup. Turned the key on and no fuel flow. Hmmmmm, checked the fuel pump fuse which looked good and then the fuel pump relay which "appears" to be functioning. (use a jumper wire to apply voltage and hear it switch)

After reading through the several threads here:

It seems I'm left with either a fuel pump that just quit suddenly and without any warning or an open circuit preventing power to the pump. I came across a post from 2003 (near page 28) that described my situation almost exactly. Unfortunately there was no response to the post. Like the person that made this post, my engine will run if I feed it some starter fuel and the fuel rail on the engine is void of fuel or pressure.

I'm going to go out and stare at the wires to see if I can locate a break or other condition that would cause a circuit problem before deciding to drop the gas tank and pull the fuel pump.

I was wondering if anyone could point me in the right direction in terms of troubleshooting the wire / wire connections and other related fuel circuit components so I can rule them out before pulling the pump out?

Also, I tested the voltage to the e-shut off and it was about 9 volts. I was expecting 12. Is that correct? How does the switch work? I had assumed that it was simply a single line interupt of sorts. Anyway, any suggestions would be great. She's a great rig and I love driving her. With all the trim faded, the clear coat and paint flaking off in large sheets, she "looks" like a POS, but until this problem showed up she'd out do any 2006 rig around here in both performance and gas usage!!!

Updated Entry:

I popped the hood and trunk, and decided to try and start it in neutral (like I saw in another post) and guess what? It started!! I let it idle for a few minutes then took it around the block. Ran just fine. Pulled in the driveway, put it in park, shut it down and tried starting it while in park... Yup, it fired right up... So what kind of switches am I looking at to target for replacement? I remember reading there was one in or on the transmission. Can I get to that one without dropping the tranny? BTW, I did try starting it before in neutral and it wouldn't. Something has changed over the last several weeks. Anyone care to venture a guess?

Thanks...

[KimMG]

What changed?
You now have fuel in the fuel lines, you may have had just air before.
Due to lack of use, the fuel pump may have stuck.
Clog in the fuel line cleared itself.
You may have a loose or corroded connection that is going to give you intermitant problems until you find it.

[MacGyver-it]

Thanks KimGM. I was thinking the same. When the problem first presented I did my troubleshooting over two or three days. I had been driving the car everyday until then. I wonder if running the tank to such a low level caused the pump to jam or perhaps some foreign matter to obstruct the pump intake. I would like to rule out any circuit problems. Can you or anyone else tell me which wires and connections to examine?

Thanks again for your response!

[auto trainy]

It sounds like your security system did not allow the pump to run if you have one.

[KimMG]

Here's a link for some wiring diagrams

http://www.autozone.com/servlet/UiBr...3d80173da8.jsp

Although I recommend making a couple of enlarged copies from a manual. One for reference and one to make notes on as you check circuits. Take one enlarged copy and hi-light the questionable circuit, then use a pencil to mark off what you have checked. Use dielectric grease on all electrical connections to prevent corrosion. If you don't have a manual, your local public library may have one and usually libraries have copy machines.

[UNO#1]

Try hintting on the gas tank with a rubber mallet while you have a buddy try to start it. This can help free up whatever is sticking in your fuel pump. It's not a gurantee fix, but I've done it on a few cars with sucsess.

[glasser3]

ill have to try that on my mgm tomorrow

[MacGyver-it]

Thanks for the link KimMG.

I've been busy with summer business activity and apologize for the delayed response.

So far the old Merc has been running like a champ and I have not had a repeat of the starting problem. Given the cost of fuel here in Oregon, I do still tend to run the gas tank level pretty low but NOT as low as I did when I experienced the start problem.

Thanks for the circuit link. 99.9% of all the wiring I've looked over is in surprisingly great shape but I'd still like to confirm the connection integrity in critical circuits... Thanks again for all the help...

[MacGyver-it]

My fuel delivery problem has returned. Actually it returned a few months ago and I just haven't had time to deal with it. The symptoms are the same as my original post. I'm getting power all the way back to the line that feeds the fuel pump from the inertia fuel shutoff switch but I don't hear the pump running.

Should the pump be easy to hear? I've had my ear against the rear fender and stuck my head far into the trunk but can't seem to hear any whinning or any noise at all.

Since there is power coming from the shutoff switch and assuming the pump is grounded by body would it be safe to say that the pump has given up the ghost?

Any more thoughts?

[MacGyver-it]

Everything is good to the pump. Wiring looks a bit greasy/dirty but power is there. Took a suggestion from another post and tapped lightly on the bottom of the tank below the fuel pump mounting cap and it started right up.

Guess I'll need to start looking for a reasonably priced fuel pump. But in the mean time, have rubber mallet in trunk - will travel until pump taps back!!opcorn:

[dwyczalek]

Originally Posted by MacGyver-it

Everything is good to the pump. Wiring looks a bit greasy/dirty but power is there. Took a suggestion from another post and tapped lightly on the bottom of the tank below the fuel pump mounting cap and it started right up.

Guess I'll need to start looking for a reasonably priced fuel pump. But in the mean time, have rubber mallet in trunk - will travel until pump taps back!!opcorn:

About 200.00 just for the pump I replaced one on a 87

[MacGyver-it]

Yeah, I couldn't find anything for less that 200 bills so I decided to pull the puppy out and give it a good cleaning. I thought I'd be able to rebuild it but once I got it out I didn't see any way to do a rebuild. Instead I just ran brake cleaner, a bit of Chem-12 lubricant and air through it until it ran smoothly and quietly. I was surprised at how much gunk I managed to dislodge. It's been running fine for the last 4 months.