Lancia Beta 2liter carb version - possible fuel starvation?

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HFStuart
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Lancia Beta 2liter carb version - possible fuel starvation?

Post by HFStuart » August 6th, 2007, 8:56 pm

I've got a problem with my Lancia Beta Spider 2000. The symptoms are similar to fuel starvation but I'm not convinced.

The car runs on Bosch electronic ignition. It has a new fuel tank, cleaned out carb new fuel filter(s) and a low pressure electric fuel pump. I tested the pump today and it's producing about 18 Gal / Hr at the carb fuel inlet - so if it is fuel starvation it's not down to the pump or lines. Additionally the in line filter between the pump and carb always has fuel in it.

When the car is hot the engine stalls and cuts out if you run it under anything other than very light load. This happens at low engine speeds as well as high so it cuts out at 50+ in top or when climbing hills at lower speed in lower gear. It stutters first and then cuts out completely, there's no response at all. The rev counter stays on suggesting that the LT side of the coil is fine. After coasting for a few seconds (or backing right off if the car hasn't stalled completely) it always restarts.

When the engine is cold it runs perfectly (other than it looks as though the thermostat isn't closing properly - again). I can run on high load for as long as I want and there are no problems - this I mainly why I don't think it's fuel problems I can't see how that would only happen on a hot engine.

Any ideas?

Thanks
Stuart

HFStuart
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Post by HFStuart » August 7th, 2007, 8:15 pm

Well it's unliklely to be a tank vacuum, HT / Coil leads distributor cap or rotor arm problem.

All replaced / tested today

Next up coil & ignition module (thank unacceptable they're not expensive bits)

It died whilst idling today when I was warming it up prior to taking it out. If it was fuel starvation would I expect the revs to rise at all as the mixture got weaker before it died ?

Stuart

Guy Croft
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Post by Guy Croft » August 9th, 2007, 9:10 am

Sorry, no idea of the true cause, keep going thru it all step by step, the ignition system is easy enough to test on the bench with a car battery. FWIW I have never known a Bosch module to fail, the distributor unit - yes.



GC

sumplug
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Post by sumplug » August 9th, 2007, 2:21 pm

The clues are in the cold running and full load running [both chokes open]. You perhaps have a problem with the primary choke system. I think you need to set the carb up as its sounds like basic settings of the base plate are not right. Has the carb got an adjustable power valve jet [Weber DAT]?
As it starts instantly when it stalls, i would eliminate overheating Relays or connectors. But check all wires to the distributor. What carb is it??

Andy.

HFStuart
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Post by HFStuart » August 9th, 2007, 5:08 pm

Andy / Guy

Thanks for the encouragement.

Apologies, perhaps I wasn't clear - when it stalls it doesn't run on either choke. It's a 34 DMTR

The coil will be replaced with a new one tonight. I'll try to get hold of a known good module as solid state electronics seldom fail (as you said Guy) and new ones aren't cheap.

Then I'll be on to the distributor and checking for broken wires.

Stuart

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Post by sumplug » August 9th, 2007, 6:58 pm

Right, DMTR carb a nice carb. Maybe the float has wrong setting, or the fuel pump is pressurising the float at low throttle openings, causing the stalling.
Have you checked the fuel pressure? Is the throttle stop adjusted correctly?
Have you had all the jets out and blown the jets/galleries through?

Andy.

HFStuart
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Post by HFStuart » August 19th, 2007, 9:36 pm

I finally managed to nail this today, or at least the cause. It died while idling and I whipped off the top of the carb (goodd tip Guy) to find empty float chambers.

The thing is I'd spent the morning replacing the fuel lines, filter etc etc. As a last resort I disconnected and plugged the fuel return. Bingo, problem solved. What I suspect was happening was that the 6mm return line in combination with my low pressure 1.4psi pump was resulting in too little pressure at the needle to fill the carb - so the pump was happily circulating the fuel with relatively little actually going in. unacceptable knows why it only happened while hot though.

Anyway do you think the 34 DMTR will be OK with 1.4psi feed and no return ?

Stuart

Guy Croft
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Post by Guy Croft » August 20th, 2007, 5:29 am

Good post - I always wondered what happened with the fuel return in that event and at last I have the answer.

Well done!

GC

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