1990 w/ M20 No Start in Supercold New England

[gjmascoli]

Recently had to replace the fuel pump which had eaten itself alive. At same time replaced: Fuel Filter, O2 Sensor, Plugs (Bosch Coppers), Air Filter.

Car ran noticeably better, a lot revvy-er, more power, no more hesitation (which seemed like a vacuum leak but was prolly the pump).

But, fuel economy worse...started at 19mpg mixed driving, then down to 18mpg, and perhaps lower.

Also, the new pump introduced a new problem.....engine would start right up when cold, but cough and stall unless I blipped the gas. Once ith "caught" it would run fine.

Now to current state: yesterday morning, 8deg F, crank and crank, no start.

I'm guessing I'm not getting any fuel. I'm not with the car so I haven't done any trouble shooting, but guessing:
- fuel pump fuse blown?
- fuel pump relay?
- fuel pump dead?
- clogged new fuel filter?

I will try to check these out and also try to check fuel pressure.

Any other ideas / thoughts? I always love the input from this forum.

[ross1]

What sort of fuel pump?
check the fuse, if good test pressure.
Unless you have a whole lot of debris in your gas tank it isn't a clogged filter. I've seen twenty YO carts still sporting the original filter
Were it not for already suspected fuel pump problems I'd call it flooded. Pull a spark plug and see if it's wet.

[gjmascoli]

Brand new Bosch fuel pump, correct part number, I pulled the P/N from the old pump before purchasing the new.

Haven't tried t restart....is possible it flooded for some reason, although has never done so before.

I did have to clean out some aluminum shavings / debris left from the old pump. Basically the old pump cracked its housing and created some shavings, but the fine mesh filter mounted on the pump was effectively protecting the old pump....I cleaned out everything I could get.

[gjmascoli]

Fuse good, still no start.

Will do following:
- jump relay terminals 30 to 87 to see if pump runs. If yes, will trouble shoot relay. If no, bad pump or not getting voltage to pump. Will check voltage
- if pump and relay are good, will move on to pressure
- if pressure is good, i guess fuel delivery rate, but I suspect I will find the problem prior to getting here.

[gjmascoli]

Did the following, all with no response at the fuel pump:
- Jumped relay terminals 30 to 87, pump did not run
- Voltage at pump 11V (it is 5degF and I am getting 12V across the battery terminals)

So, pump dead.....question is why. Oh well, back to draining 20 gal out of the tank and putting in another pump.

[gjmascoli]

OK, so I'm not as good as I thought on diagnosis.

Got a new pump and installed today in single digit windy weather.

Still no start

To make matters worse, the old pump does work now that it is out of the tank and I connect 12V directly to it.

So........potential issues:
1) The Bentley says I should read Voltage from the Fuel Pump/Level sender terminals 4 & 5 on the harness connection at the pump. I get 0V across those terminals, but I get 11V at Pins 1 & 3. Now that I think about it, is that just telling me that my level sender is getting power?

2) I get the same result across terminals 4 & 5 (0 V) and 1 & 3 (11 V) with the Fuel Pump Relay installed and the key turned to "run"; I also get that result if I remove the Relay and jump relay terminals 30 to 87.

Can anybody tell me if I am getting the expected / normal results here? At the moment I'm thinking that somehow I am suddenly getting no power to the pump, but why would that happen suddenly? Fuse #23 is OK.

I'm not even close to checking fuel pressure because I don't seem to be getting the pump to run.

- Bad relay? But that doesn't explain why I get nothing when I jump the relay terminals.
- could the new fuel filter be clogged?
- ice in the system? It is really freaking cold but this hasn't been an issue in the 7 years I've owned the car

Thanks in advance

PS
I just saw this post...
https://www.bimmerforums.com/forum/s...rt-thread!-M50

I guess it is possible that I have a flooded engine, or a bad CPS......

[katit2]

Well. Can you jump fuel pump? Supply direct power and see if car starts. If so, then you at least know where to look next

[gjmascoli]

Katit2
That is a good idea. I'd do it now but it is 9pm, 0degF, and the wind is blowing!

But I do expect I can find a way to get 12V directly to the pump. Thanks for the idea.

[gjmascoli]

UPDATE:
After being away for the week of 1/8-1/14 and then a normal workweek preventing any diagnosis, this morning, in a balmy 40ish degrees the car started right up!

Obviously moisture in the fuel caused by a bad seal between the fuel level sender and the tank. I fixed this when I replace (the perfectly good) fuel pump. The weather had been warm around the 13th and 14th, touching 55F and we never got back down to single digits. Must have been enough to unfreeze the glacier.

So we are back on the road.

[ross1]

UPDATE:
After being away for the week of 1/8-1/14 and then a normal workweek preventing any diagnosis, this morning, in a balmy 40ish degrees the car started right up!

Obviously moisture in the fuel caused by a bad seal between the fuel level sender and the tank. I fixed this when I replace (the perfectly good) fuel pump. The weather had been warm around the 13th and 14th, touching 55F and we never got back down to single digits. Must have been enough to unfreeze the glacier.

So we are back on the road.

Glad that you are again ambulatory again. Are you saying the reason the car wouldn't start is because of water in the fuel?