Fuel pump does not run when key is turned

Segler

New Member
Hello,

When I turn the ignition key in my 1989 E28, Universal M2-12, the electric fuel pump is supposed to run, correct? Mine does not; has anyone had experience with this?

The background of the question:
My engine was running great when I decided to drain the primary fuel filter bowl for the first time (for me). I did not bleed the fuel line afterward. The engine then ran but would quickly stall.
I did some searching in this forum and figured air had gotten in the fuel line and I needed to bleed it after all, so I bled the primary fuel filter using its built-in manual pump. Then I turned on the ignition and opened the bleed bolt on the secondary fuel filter. Nothing happened because the fuel pump didn't (doesn't) turn on. I cranked the engine a few times then (not long), but no fuel ever came out of the secondary fuel filter bleed hole. But that must have let in even more air, because now the engine won't start.

I've read many helpful posts here that talk about running the fuel pump to bleed the lines; how do you get the fuel pump to run when the engine isn't running?
Thanks for any ideas!
Eric
 

Christian Williams

E381 - Los Angeles
Moderator
Blogs Author
Since your starter motor works, there is power.

The electric fuel pump is wired to the ignition system, so maybe there's a bad connection or loose ground. Sounds coincidental, but wires get dislodged when we're working on stuff.
 
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Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
With the key "on" put your little multi-meter across the connectors on the electric lift pump. Voltage should read the same as your battery voltage, which you can verify with the same meter.
These meters are quite inexpensive these days, so it's good to keep one aboard.
 

Kenneth K

Sustaining Member
Blogs Author
My lift pump has a "disconnectable" spade connector in the positive wire feeding the pump. I'd start at the pump and trace both the positive and negative leads back to their sources. An "unplugged" spade connector would be a 30-sec fix.

On my engine, the fuel pump is fed from the "purple" wire that goes to the alternator for "excitation" voltage. A splice into this purple wire feeds a red wire to the spade connector, which ultimately feeds the positive side of the pump.
 

Segler

New Member
Resolved

Ken was correct! One of the two connectors that plug into the bottom of the fuel pump had come off, and since the bottom of the pump isn't visible I didn't see it at first. Plugged it back on and the pump now operates when I turn the key. Thank you Ken, and all who replied!

There is another interesting aspect to this though, which is that the engine still ran with this connector off. Before I discovered it was disconnected, I was able to start the engine again by working the little manual primer pump knob on the primary filter (which Christian hates and I now love) about 130 pumps. The engine then started and I ran it about 25 minutes. I stopped and started and ran it two more times with no problems before I reconnected the connector.

How could the engine run with an incomplete fuel pump circuit? I can only guess the injector pump is strong enough to keep the fuel flowing except at idle when cold (and lower idle rpm), when it was stalling before. Is that a plausible explanation?
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
Ken was correct! One of the two connectors that plug into the bottom of the fuel pump had come off, and since the bottom of the pump isn't visible I didn't see it at first. Plugged it back on and the pump now operates when I turn the key. Thank you Ken, and all who replied!

There is another interesting aspect to this though, which is that the engine still ran with this connector off. Before I discovered it was disconnected, I was able to start the engine again by working the little manual primer pump knob on the primary filter (which Christian hates and I now love) about 130 pumps. The engine then started and I ran it about 25 minutes. I stopped and started and ran it two more times with no problems before I reconnected the connector.

How could the engine run with an incomplete fuel pump circuit? I can only guess the injector pump is strong enough to keep the fuel flowing except at idle when cold (and lower idle rpm), when it was stalling before. Is that a plausible explanation?
In warm weather our former Universal 23 hp diesel would run some of the time without the electric lift pump operating. Evidently having the fuel being forced into the high pressure pump at about 3 psi is needed for higher flow and rpm's but not absolutely vital. While trouble shooting some starting problem that turned out to be *low voltage to the Facet pump, I found out this confusing bit of trivia.
Diesels are simple devices.... but yet they do have their quirks. :nerd:

*part of the whole Universal wiring harness problem.
 
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Christian Williams

E381 - Los Angeles
Moderator
Blogs Author
I'm glad you have bonded with the Racor pump. This is clearly a case of different strokes for different folks.

Actually, the electric pump (when connected) will eventually prime the system, using the bleed valve--and it all goes faster if you fill the Racor filter bowl with fuel before reassembling. Which, given the awkward location, also means spilling some, of course.

And if we forgot to say it, welcome to the forum!
 

Kenneth K

Sustaining Member
Blogs Author
There is another interesting aspect to this though, which is that the engine still ran with this connector off. Before I discovered it was disconnected.
My boat has a fuel shutoff valve near the electric fuel pump. Don't ask me how I know, but the engine will run at low speeds for 15-20 min with the fuel valve closed.....
 
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