924Board.org

[Mafo]

Good morning all, hello, I am new to the forum and looking forward to testing your knowledge and experience of our newly acquired genuine "barn find" 924 Turbo. This is my first Porsche project and i'm looking forward to it. Over the years I have worked on a number of different cars and have found no better workship manual than the "knowledge of the crowd!".

So we acquired the turbo from its previous owner having had it dry stored for some 17 years. It's pretty much complete - albeit completely stripped and in boxes! The car also thankfully came with a tonne of spares.

it wasn't until we got it back to the workshop that we found the underside had been completely rebuilt, it is like a new car underneath will all bushings, brake lines, fuel lines, suspension components and brakes and completely rust free. So very very pleased! Interior is choclate brown, all leather tomb stone seats tcomplete with alll original interior parts too.

Not rushing the "will it start" (those videos make me cringe!) we set about working through the basics. We went to drain the tank of old fuel, only to find it had been dry stored with an empty tank! There was some residual fuel left in the lines to the tronic system. So, we popped out the sender and used a borescope and the tank appears to be rust free. The lower part of the tank had some residue, but overall it was in good shape.

The in tank pump appears to have failed. It's the ridiculously expensive one.
The in line pump appears to have failed. Both look like the original parts.

I have SO many questions, but before I get into those, I would really like to get the full low down on replacement pumps. So far from my research I have come across and read up on a number of suggestions:

1. Replace in tank with 944 strainer and fit inline pump
2. Replace both pumps OEM
3. Replace in tank with 944 strainer and fit upgraded inline pump
4. Leave old pump and fit upgraded inline pump

I'm leaning towards number 3. What I am really looking for is for peoples input who have done any of the above, pro's and cons and if they have upgraded pumps, what brand / output pressure did you opt for? Any starvation issues or fuel pump relay nuances I need to be aware of?

Thank you!

[chuck21401]

What problem are you trying to solve?

I'm running one external fuel pump on my 924 turbo (not sure which model fuel pump, it was there when I bought it). I was having some troubles so I drained the tank and checked the 944 strainer...wasn't clogged. I think my issues related to low voltage getting to the fuel pump.

I'm not sure an upgraded fuel pump is needed. I'm running 12psi -14psi (with an intercooler) and the fuel system seems to keep up just fine. When I'm on boost the AFRs dip into the high 10s according to the gauge. I've also checked my fuel pressures with the CIS pressure tester and everything is with range.

You'll find a number of posts in the 931 specific forums related to fuel pumps, fuel pump relays, grounds, relay board and more.







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1981 Porsche 931 w/S1 engine & g31 transmission. Water-cooled intercooler

[Raize]

I had a "failed" in-tank pump once where one of the wires had just broken off at the solder joint and needed to be re-soldered. Worth checking.

You can actually go further into rebuilding them, but I've never tried.

[Beartooth]

I took my in-tank pump apart and messed around with it a bit, but I'm not sure I could get it to function again, or if it's even worth trying. It was very badly gunked up though. If you're trying to get one going, I'd experiment with soaking it in solvents and fuel system cleaners before I opened it up; it might do the trick, and probably won't ruin it, vs. high probability of coming out with nothing more than a small pile of parts if you take it apart.

If fuel supply is a concern, there are higher-flow Bosch pumps available (Bosch 580464200 - I think the same pump as the Bosch 61944 - is one), but I can only see needing an upgrade in a car that's either running a lot of boost, or E85. I'm also just running a basic Bosch pump, and I seem to have good fuel supply and no issues with no in-tank pump. I think it's mostly called for to ensure the main pump gets primed after running out of gas, and possibly helps with near-empty situations. So unless you're planning on running around hard with the tank just about empty, or running out of gas occasionally... So far, mine's primed just fine too. I do put a full five gallons in when I've had to drain the tank though, and crack the pump outlet until I get a little gas to make sure though.
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1980 931 diamond in the rough