Upgraded primer pump question.....
 

In the directions, it says to use Loctite 683 on the threads of the pump. Since there is a copper washer, why use more sealer? If you used it, how did you get the fuel out of the lift-pump cavity when you removed the old primer pump, did you clamp off the lines and suck it out with a syringe? Finally, where in the world can you find Loctite 683?

Just snug it up tight enough to firmly(be sensible) compress the Cu washer a bit. Loctite 683 shows "no match" on their website. I've always just screwed the primer pump in and it works and doesn't leak. Great improvement in design over the old style. DON"T stick any sealant down into the IP. Just screw the primer pump in using the Cu washer and you'll be fine.

I installed the new primer pump without loctite and there are no leaks.

There was one advantage with the old style pump. I could tell by pumping it which filter was plugged:

1. Handle pulls up hard and goes down easily, primary filter (in-line) filter plugged.

2. Handle pulls up easily and goes down hard, secondary filter plugged.

However, I do like the convenience of the new primer pump, no need to unscrew the handle.

P E H

I'm involved in the replacement primer pump installation now on the 1984 300SD.

The instructions call for Loctite 638 retaining adhesive.

I have not taken the old pump off yet and cannot confirm fitment, but the new pump comes with an adapter ring. That is, the pump is a smaller diameter that screws into this adapter - the impression is that the adapter then screws into the car where the old pump fit.

The pump-to-adapter is sealed with a copper washer gasket.

Its the threads of the adapter-to-car interface where they want you to carefully clean and use the Loctite 638.

First question would be, is the adapter necessary for the 616/7 application?

If so, then the second question is how did you seal it?

Guess I'm good to go if the adapter ring is discarded. :)

Ken300D

I don't remember directions when I put the new primer on mine (I'm not a good direction reader though). I know I didn't use loctite though and it's never leaked a drip in 20,000+ miles.

ttt

Just interested to know if anyone remembers using the size adapter ring - or if just the primer pump without an adapter threads into the injection pump.

Ken300D

When I installed the primer pump I did not use any adapter ring. It threads directly into the injection pump.

Roman
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86 300SDL 207K
83 300D 219K
80 300D 138K

No adapter or locktite on mine and all is well. Easy replacement.

Thanks for the helpful information.

I attempted the job yesterday but did not really have the tools with me to do the job (car is stored elsewhere). There is a lot of interference from the power steering hoses, etc. Plus the old primer pump seems to take a really big wrench, maybe 25mm?

So, I'm looking for tips on what tools to use to take the old primer pump off. One idea I had was to fully remove the fuel pump assembly with the primer pump and work on it off the car. Would hate to do that. Maybe a pipe wrench or vise grips on the body of the primer pump?

Plus there is a lot of wrench interference from the fuel input and ouput connections.

I'll do a search through the archives, but also interested in hearing comments on this,

Thanks,
Ken300D

Hi Ken.

I used a Vice grip and some elbow grease(if needed
you can hit the Vice grip with a rubber malet to break it loose)
and since your not going to reuse the old style pump
it doesn't matter if you damage it.

Use a short handled wrench to tighten the new
pump.

That is how I did it.

Unfortunately the new one I installed didn't work,
it seemed as if it wasn't pumping at all.



Louis.

from what I remember doing mine
 

It was a PITA to get mine off. I ended up having to use vise grips to get a good grab ont the old one due to the wierd angle b/c of the hoses as you described. It finally broke free. You might get a can of "liquid wrench" and let it some some before you tackle it again.

My old primer pump just made a mess as you pumped. I love the new unit much better...

I upgraded mine a couple months back. It didn't come with an adapter, nor was one required. There were no instructions to use loctite or any other sealant. Crows foot wrenches make it a very easy job. Good luck.

Just completed this job. The size adapter ring that may come with the upgraded Bosch primer pump is not used - so you do not need any Loctite 638 sealing adhesive.

A plumbing faucet wrench is the perfect tool to remove the old original primer pump. Just grab the body of it with the faucet wrench and you'll have plenty of power to loosen it.

The new Bosch primer pump will tighten down with a 17-mm wrench. I used a short stubby wrench from my motorcycle tool kit. You could also do well with a crows foot wrench.

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On a side note, provided the original primer pump is not leaking, you don't need to disturb the primer pump to reprime the system when replacing the main spin-on fuel filter. Run the car to operating temperature. Fill the new filter with diesel fuel before putting it on - car will start and run just fine without priming. Even better, use something you know is clean like Diesel Purge from the can - you have to be very clean.

Ken300D

If you are trying to fine the faucet wrench refered to by Ken300D, you'll find them usually called a basin wrench at hardware stores. Most experienced clerks will know the tool by both names, but manufacturers will mark them basin wrenches.:)