Hello again,
My 90 240 and my 83 were both stalling lately while out during the hots days here in New Mexico.

I tested the both fuel pumps in the 90 240 at the fuse 4 and 6 and the in-tank pump was not working, main pump was working. I installed a new in-tank pump and it has been running fine for a couple of weeks now.

I tested the intank fuel pump on the 83 240 at the fuse 5 and 7 and the in-tank pump was not working, main pump was working. I removed the in-tank pump and tested it, it was dead. This morning I installed a in-tank pump and tested it at the fuse 5 and 7 and it works. I also installed a new fuel filter which it needed badly. I went to start her up and she cranks, but does not start up.
I tested the pumps and now the main pump is not working. I jumped fuse 7 to five with-out fuse five in and the intank pump works but not the main pump.
I got under the car and the main pump was hot and the fuel line that goes from the tank to the main pump was hot to the touch and the gas felt like it was boiling. I removed the jump and tested the power at the main pump and it is getting power.
What could of caused it to go out at this odd time.

Thanks for any advice,
Joseph Segura

Hi again Joseph,

You're on a roll there, replacing dead tank pumps. I feel like a kindred spirit this summer.

The problem you describe is an unfortunate one. The main pump getting hot, but not running, must result from something keeping its armature from turning. It is possible it is a coincidence, but my first suspicion is a piece of debris made its way through the large hose from tank to pump and wedged in the pump's close tolerance cam roller chamber, locking the pump's rotor.

There's no filter but the sock before that, so it stands to reason the debris was broken loose somehow in the replacement process at the tank.

I think you will be dropping that basket again and replacing the main pump. I am sorry. Just double check after it has cooled some, and be sure you have good power at the pump terminals, but that may be wishful thinking. Sounds like you already checked thoroughly.


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Art Benstein near Baltimore

You never really learn to swear until you learn to drive.

If like Art said something may have come through the Large hose it my well be a piece of the large hose if the hose is old.If so replace the hose when installing new main pump.Charlie

Charlie,
I replaced the in-tank pump and this caused the main pump to
fail because as Art said ...........

The problem you describe is an unfortunate one. The main pump getting hot, but not running, must result from something keeping its armature from turning. It is possible it is a coincidence, but my first suspicion is a piece of debris made its way through the large hose from tank to pump and wedged in the pump's close tolerance cam roller chamber, locking the pump's rotor.....

The jam in the main pump was probably something broken lose inside the tube that leads from the in-tank pump to the main pump when I turned on
the 'new' in-tank pump, which had probably been broken for years and had build up in the hose that was pushed loose by the 'new' in-tank pump. And this
probably caused the main pump to lock up, get warm and cause some alarm.

So from now on if I ever replace a in-tank pump that may have not been working for some time (years) I will remove and replace that hose so as to avoid breaking the
main pump with this build-up.

Hopefully the blockage is something that can be removed and hopefully the main pump will then run as expected.

I will let you 'all know what I discover tomorrow when I pull the main pump off.
I was going to do it tonight, but it took me 2+ hours to locate my spare main pump (in trunk in 240 that is parked at my sister's house).

Thank you all for your advice, it eases the pain.
Joseph Segura

If you do decide it was the hose internally deteriorating, please let us know how it looked and what you used to replace it. I haven't seen one yet falling apart inside (or out) so I haven't replaced one. Neither have I found a good source for one, so I instinctively avoid using pinch-off clamps on them.


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Art Benstein near Baltimore

I have six locks on my door all in a row. When I go out,I lock every other one. I figure no matter how long somebody stands there picking the locks, they are always locking three.

Hi Art,
I am not sure why the main pump went out, the fuel hose seemed fine.

What I did find is that the broken pumps fuel entry tube did not have
a propeller deep inside the plastic entry tube simular to the replacement pump.
Also, on the metal exit tube on the broken pump there is what looks to be
a wound up spring pushing outwards inside that tube on the end of the pump
that has the 2 power ports.

I was looking for diagram of a fuel pump on the internet and I could not find one. I want to know how they work and their various parts.

The newer main pump is humming along great.

Does anyone know why the newer 240's pumps click on for a couple of seconds when you turn the key to position II and the older models don't?

thanks for your knowledge,
Joseph Segura

Hi Joseph,

You're moving right along.

I didn't expect the hose to be deteriorated. I think a very small piece of rust or debris could jam the rollers. The only way you will know is to peel the pump open and look for yourself.

Here's something I found on the net supporting this: bosch pump contamination

Here are some shots I took of inside an 83's pump. You'll see the guts won't tolerate a large hunk of sand.

I doubt any of us know for sure why the "prime" pre-run is done. It isn't needed for operation, though it makes it nice to hear when troubleshooting, as in "does it run for a second when you turn the key". The notion of priming or pressurizing the rail seems wrong because I noticed after depressurizing, a pressure gauge indicates full pressure before the engine even cranks one rev. The K-jets did it, presumably because of the large accumulator, but then LH2.0, and LH2.2 abandoned it. LH2.4 returned with the majority of program chips restoring that feature, but not all. I still tend to call it "priming".

The spring sounds like the check valve on the outlet. The impeller on the input sounds like a feature on a different model pump than what should be on that car.










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Art Benstein near Baltimore

Have you ever noticed? Anybody going slower than you is an idiot, and anyone going faster than you is a maniac.

Hi Art,
Thanks for getting me information on this problem.
I will open the broken pump soon and hopefully figure out what went wrong.
I am guessing it was hidden crud in the pre-pumps sock, I got both at the
pick and pull and the sock looked original but looked good too.... but I should
of bought a new sock.....okay I screwed up. I was in the trunk when I
realized I did'nt get a new sock and thought 'oh this one looks okay'...
my mistake.

The main pump I installed was probably from a post 1983 240, but like the
sock it looked good and like the one in the car.

So far so good....
She runs super now, starts on the first try, and seems to have more power
and spunk...

Thanks again for being there and for your kindness,
Joseph Segura in New Mexico

Hi Joseph,

I re-used half a dozen socks, only replaced one when it was ripped. Most come out looking good as new. I wouldn't expect crud to be in the sock. I also prefer the prices at the yard.
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Art Benstein near Baltimore

Why do we choose from just two people for President and fifty for Miss America?

Hi again Art,
I will hook it up again and try to tap it loose.
I have a back up from the salvage yard I will wire
up if my first cure does not work.

Thanks again my buddy,
Joseph Segura

On your 83 hows your wiring harness ,has it been replaced? You know this falls in the years of the bad wiring harness?

I replaced the harness in the engine last week.
Actually took me a couple of weeks... I pulled the bad
one and stalled on installing the new one for fear
of screwing it up. But, I got it on the first try...
Just lucky I guess.

Joseph Segura