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T-Series SU fuel pump fun

NutmegCT

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Just wondering if anyone can advise, or point me to troubleshooting sources, on my Type L SU fuel pump.

Issue: no more steady click/ticks. Just a rapid fluttering/whirring sound.

Thanks.
Tom M.
 

Flash_Harry

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Dave DuBois - on another forum - has this article posted on SU fuel pump troubleshooting:

https://www.mgexp.com/article/fuel-tsg.html

Not sure if he still does refurbishment of SU pumps, but this should get you a start on the problem.

Harry
 
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NutmegCT

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Thanks Harry. I just contacted Dave D.

Problem is probably the old (original) diaphragm, which I could replace myself. I'll hear what Dave has to say.

Tom M.
 

DrEntropy

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Diaphragm compromised by that demon ETHANOL.
 
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NutmegCT

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Ethel who?

Photo of the diaphragm:

IMG_0046.jpg
 

PAUL161

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Might make a nice wall decoration, for a remembrance piece! :highly_amused:
 

pdplot

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When in doubt - change it out.
With the three TDs I had, none of them had any SU fuel pump trouble. And the Mark II had 2 of them. If it kept clicking, you had a fuel leak.
 

DrEntropy

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Now that it's apart, change the diaphragm. The membrane appears to be intact but the cloth re-enforced rubber part looks dead.

As pd has said, there's something else wrong. Look to the carb's float bowls and needle valves, including the floats themselves. Pull the line from the carbs at the supply pipe and block it off, turn the iggy on and see if the pump slowly stops clicking. If not, start looking at the line from tank to pump for air leaks and consider the idea the in-tank pickup may be rusted (pinholes). Fill the tank and see if things change.
 
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NutmegCT

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Thanks Doc. I'll replace the diaphragm soon as I get the old one out and can measure it. There are two sizes (3" long and 2 3/8" long).

Here's "the rest of the story".

After draining and washing (and rinsing and drying) the fuel tank two weeks ago, I hooked up the lines to make sure there were no clogs or crud anywhere in the fuel system.


Ignition on, pulled the starter switch. Cranked it up - engine started fine and dandy. But died in about five minutes.


Cranked again - started fine, but this time it died in a few seconds.


Then I noticed that when I turned on the ignition, the SU pump didn't click. Just "buzzed" or whirred.

Oy - must have a clog inside. Disconnected the line from pump to the carbs, ran the pump - nothing came out, and the pumped just whirred and fluttered again.

Removed pump. Girding my loins, I pulled it, opened it, and blew air through the inlet and outlet. Diaphragm looked dodgy, so went through the fun of trying to diagnose if it had just gone bad. Being a complete dolt (dotard?) about SU pumps, I was treading carefully. But other than the wrinkled appearance of the diaphragm, pump seemed ok. Gave it 12 volts, but it still just whirred without clicking.

Decided with the pump off, I'd check for crud in the fuel bowls. Managed to get the bowl tops off, removed the floats, cleaned the bowls, reconnected everything.

Ignition on, pump just fluttered again. Didn't pull any fuel through the line; bowls stayed dry.

Well, maybe there was still some crud at the bottom of the fuel tank that had lodged somewhere in the fuel line.

Blew air through the line - noop - no fuel line clogs.

Want to guess why the pump was whirring and not pumping fuel?

:jester:
 

DrEntropy

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The pump's points.
 

JPSmit

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Well there is a first for this site :rolleyes: well spotted
 

pdplot

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My dad's answer to a tv or radio problem- "Are you sure it's plugged in?"
Not as bad a problem as failing to put oil in after draining old oil.
 

DrEntropy

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'k Tom, you now owe me a keyboard.
 

DrEntropy

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My lesson unlearned is; that you can't leave the dizzy rotor on the bench and expect the thing to start. I relearn that one more often than I'd like.
 
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