cfc928gt

Both of the pumps on my '89 aren't working. I've read through the old rennlist posts and it appears many have reported problems with the in-tank pump that is used on '89 and newer sharks. I would suspect it's the failure of the in-tank pump that ends out destroying the outside main pump through either fragments from the failed pump as it destroys itself or because its not working acts somewhat as a restriction or blockage thus causing the main pump to work harder. Does it really need two pumps? Do owners of earlier cars, especially '87 & '88 S4s have any fuel delivery or pump failure problems because of only one pump? I would think putting in the fine mesh screen in place of the in-tank pump as some have done might be the best solution. Failure of both pumps in only 66k miles is unacceptable to me. Thoughts?

John Speake

The two pump system was generally fitted to "hot climate" markets where the risk of vapour locks was considered to be higher. Some markets only had the one pump.

One of the reason for the higher duel pressure on the S4 compared to the earlier cars was to lessen the risk of vapour locks.

I just had a French customer who has lost 2 main pumps in a couple of months. Your debris theory sounds likely !

Jim_H

Seems the inline pumps rubber hose tends to disenegrate over time. As this happens tiny pcs of rubber can plug the first or second pump. I have pulled pumps out of 2 different Sharks with less than 70k. Both times the filter almost broke off in the tank. I try not to run my Sharks below 1/4 tank in the hopes that filter won't bounce around as much.

I asked Jim B about removing the inside filter and he had some good reasons not to. Hopefully he will chime in here. I would love to eliminate the blasted thing. It is the only part that has ever left me stranded.

Susan K Thomas

The in-tank pump provides a stable source pressure for the main pump, decreasing cavitation and increasing performance and longevity of the main pump.

But yes the hose on the intank pump does fail due to contaminants in the gas. We add in-tank pumps to all modified pre-89 cars and it greatly improves performance of the vehicle.

Jim_H

Are they the stock in tank pump or are you using an aftermarket?

TIA

cfc928gt

Jim_H, great picture! Unfortunately, I've seen several pictures of these pumps with the hose split and in the archives there are numerous stories of exactly that happenning. I also was stranded by this failure in traffic and I'm not anxious to just redo it like it was considering how many low mileage pumps going out that I read about in the archives.

Susan, if I read what you said correctly, you add the in-tank pump to modified earlier cars and it greatly improves performance. In what way? Does it actually increase HP or TQ? Just trying to figure out if there's a better way...

SMTCapeCod

My '83 RoW had not intank pump and it appeared that hte tank hadn't been cracked open...but nearly 20 years had already passed when I got in there.

The car is a coded for "Austrian Equipment" that no one has been able to help me figure out-- maybe it was to lose the tank pump .....just kidding.

Susan K Thomas

Yes, we use the factory and/or OE pump, it is made by Valeo (not bosch). On cars that are modified, when we dyno them and have problems getting enough fuel or the car is running lean, adding the intake pump will often be just the trick.

Jim_H

What are the limits to the system? Can the dual pump system handle 500 rwhp?

Thanks!

Susan K Thomas

You have to go to a higher output main pump with the same in-tank pump

Jim_H

So 500rwhp is stretching the stock system? What is the point where you want to go with a higher output pump?

Do you have a recommendation for the higher output pump?


Thanks Again!

m21sniper

There is something about women that know hotrods and sports cars that is just wildly alluring.

You go Susan.

Susan K Thomas

Yes, at 500 rwhp you should have the higher output pump. I think we usualy recommend it for anything over 450 rwhp. I will post more details when I get in to work.

Thanks m21sniper

Susan

sublimate

I've used one of these pumps and it worked well:

Several different flow/pressure curves depending on how much HP you're making.
http://www.autoperformanceengineerin.../ext_pump.html

It fits right in the stock spot. The 10mm thread at the outlet hooked right up to the hardline to the filter and I got the 12mm OD fitting for the other end to connect to the tank.

Susan K Thomas

The high ouptput pump is our part number DVK110044. We have them in stock for $395.00.

Susan