Engine stalls under load
 

Hi, I need your advice...

Today, I drove to the Alps (Northern Italy) from the Netherlands. About 900 km, 560 miles. No problem. Couple of times >200 km/h, car runs very well, boost or no boost. Engine runs very strong.

End of the day we finally arrive at the first mountain pass. Happy, happy, joy, lets get it on!

Up the mountain, under load, the engine cut out 4 times. Under load is not under boost. Car stalls, rolls to 20 km/h and then the car can be started again. Starts fine. Down the mountain, no problem (but also no load/boost).

Removed the engine last winter. Installed a new clutch, new plugs, wires, fuel filter, accumulator, check fuel pressure, etc, etc.

Any advice where to start?

Assumption: only thing I didn't change were the two fuel pumps. Maybe, after 12 hours of spirited driving, they are too hot?? Any help is appreciated.

Try a new fuel filter?

First I thought it was a 'current' problem (no electrical power), but I lean more towards a full starvation problem. Filter was changed last winter... But I'll put it on my list as possible cause.

Begore I left, I replaced the overboost relay and delay cutoff switch. Put back the original ones this morning and so far no more ‘glitch’. Fingers crossed. 🤞

Weak fuel pump? Low pressure could cause this. Does anyone nearby have CIS gauge set?
I believe for the flow the 930 requires the inlet to the front fuel pump should have been larger. Add in a partly restricted tank strainer and I believe the inlet to the first pp is at risk of cavitation, cavitation causes rapid pump wear and failure. Running the tank low can raise fuel temp in the tank, also increasing the risk of cavitation. I have no data to support this theory.

Weak fuel pump(s) was my idea as well. But after changing back the two relais yesterday morning, I’ve driven >600 km (hard) through the mountains. No more problems so far.

Nice. I will need to purchase some spare relays for mine.
David