3B primer pump (1 Viewer)

[jaymundy]

Is there any way to test these for air leaks? Mr Zebra died on the way home today. A little roadside investigation showed no fuel in the supply line to the pump. Replacing with a clear plastic hose I could suck fuel from the tank with no trouble (by mouth, just enough to see that there was fuel there and that the supply line wasn't plugged), but pump with all my might and the fuel would only get about halfway to the pump.

I've read about primer pumps and air leaks in the system. As far as I know the sedimenter is good. No sign of damaged fuel lines or hoses. The fuel return line is tight and without holes, no sign of diesel leaking anywhere.

Two more bits that make me wonder about the priming pump....when I screw the handle back down, the fuel that I've managed to pump up slowly runs back down the hose toward the tank. When the pump is up for use, the fuel remains in the clear tube, it's only when I screw it down that the fuel runs out. Also the action of the pump doesn't seem constant...it changes feel kinda randomly. I see no sign of diesel leaking around the priming pump, however.

So....any way to test the priming pump? That's my number one suspect at the moment. Any other suggestions would be welcome also.

Cheers!
Jay

 

[duckling]

I replaced mine with a Bosch. Better than the stock unit because it has a check valve so you don't have to screw it down after priming to bleed. Black plastic top (heavy duty) and machined aluminum bottom. 4 years and no problems. Cheap too.

 

[Radd Cruisers]

Just replace it.

AVOID the cheap crap that comes from the usual places that produce low quality parts. Go for a genuine part like Bosch, Denso, Zexel etc.

I have been down the road a few times with my suppliers and some even say "Germany"on the box and "India" on the part. You really want both to say something like "Germany" or "Japan" or something like that.

I keep genuine Bosch units (made in Austria) in stock now, rather than the other junk.

~John

 

[magnus_heydoc]

dito.......

Mine was leaking after some 'overuse' and I also used a Bosch replacement. The same pump fits the diesel MB motors.

 

[lostmarbles]

Normally a bad primer pump will reveal that it is faulty by dripping diesel whenever it is operated. (But as already stated, good quality ones are cheap enough to replace simply as part of routine maintenance!)

Furthermore - There is a check valve (non-return valve) beneath the primer pump (but not part of it) that should prevent your fuel running back to your tank. - So I think you have another problem ---- most likely a leak your "injector bleed line".



A common place for leaks in the bleed line is that short piece of small-bore tubing arrowed in the pic above.

But leaks in any part of the red section often allow air to be sucked in without you seeing any diesel leaking out .... so consequently they can be hard to identify/locate.



PS. Best way to check for leaks is to use air pressure to pressurise your tank and stuff "facial tissues" around suspect areas. (When tissues get damp with diesel - you've found your leak.)

 

[jaymundy]

Gents,
Thanks! I'm going to look around for a bosch pump today. Not necessarily the easiest thing to do in Nairobi.

Lostmarbles...thanks for the tip. I'd already used the same diagram that you had posted for someone else to find a previous leak in that return line. I'll add the tissue test, though, that's a great trick.

Cheers!
Jay

 

[jaymundy]

Grumble, fool, grumble grumble, I'm an idiot.....

The fuel lines etc are all good. The fuel gauge has failed and I was sucking air from the tank. No wonder I couldn't get a prime. Not sure why I could get fuel when I sucked on the line...but I tried it again this morning and was getting mostly air. Hmmm. Add 10 liters and suddenly the primer pump primes! Hmmm.... Open the fuel sender unit access and visually look in the tank. It's pretty empty.

I did put on the bosch primer that other folks were talking about. I found one here in Nairobi this morning, first place I looked. It was a miracle. 1500 kenya shillings, or about $19, so I wasn't going to quibble.

I guess it's time to learn about the gauge system now and get it fixed.

 

[lostmarbles]

Grumble, fool, grumble grumble, I'm an idiot..... .............

Glad you got to the bottom of it.

"We're all idiots."

(Why else would we be helping each other work on vehicles that the rest of the world regards as derelict/obsolete/outmoded?)