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Re: Will not run once hot.

PostPosted: Fri May 08, 2020 9:16 am
by M.J.S
Thank you everybody, I will carefully go through all suggestions.

Now.....where's my credit card.

Re: Will not run once hot.

PostPosted: Fri May 08, 2020 11:19 pm
by denicholls2
First, you mention new coil and new electronic ignition, but you don't mention whether they are known compatible with each other. A few years ago there was a thread on just this, involving a Flamethrower coil and electronic ignition and pretty much the same behavior but the coil was finally destroyed. On the package, the manufacturer (same for both products) warned never to use them in combination, but since both had "super-best wonder device" sounding names, many people did just that.

Many years ago, I had an Audi 100 LS that did just what you describe, but would run fine on the highway and only bog and die when slowed down or in traffic. At toll booths, for example, it would die and not restart for several minutes. It ran a bit hot, but not alarmingly so. And I had a water-temperature gauge which never indicated anything like boiling temperature.

I discovered by accident what was really wrong after it died in the Callahan tunnel in Boston and a truck had to push me out while I was taking someone to the airport to catch a plane. The fins on the radiator had corroded so badly that although they looked just fine, if you brushed them lightly with your finger, they fell right off. When the engine was heated up and then lost cooling by airflow, the temperature was just high enough to cause the carb to vapor lock. A few minutes of cooling and off you could go again. Junkyard radiator, problem solved.

Re: Will not run once hot.

PostPosted: Sun May 17, 2020 9:57 am
by M.J.S
Hello Guys, just coming back with an update on your helpful advice. Thanks to all concerned.

It appears there may have been 2 problems conspiring against me.

I managed to borrow some equipment and tested the fuel pressure. It was reading around 7, so I purchased a brand new Malpassi fuel regulator and set it to a steady 2.5, which appears now to have corrected any over fuelling problems.

Additionally, by using a set of Sparkrite plug testers (why did I never own these before!), it became apparent that when running around 95-100 degrees for five minutes or so, if the engine was put under load the sparks diminished to the point the engine spluttered and died.

Suspecting now the new coil was faulty, I purchased a new Lumenition coil and ballast recommended for the Lumenition electonic ignition module fitted.

Yesterday she ran for a good hour or so without so much as a murmur, the occasional pop on the overrun, but otherwise all okay....touch wood and fingers crossed.

I'm not mentioning suppliers, but please bear in mind these parts were brand new and supposedly compatible. Mere mortals like myself occasionally have to put ourselves in the hands of 'experts' who supposedly know what they are doing, and supplying.

When stripping the ignition we tested the ballast resistor, stamped 1.6 ohms, and measured it closer to 2.5, which, according to the literature supplied, may have prematurely knocked out the new coil is less than 40 miles.

Both are now binned.

Also, I was quite shocked by the pressure the new fuel pump was pushing out, and by how easy it was put it all under control with the Malpassi. It is something I will strongly recommend to all.

Anyway guys, thanks for your advice. No doubt I may need more soon. Will keep you updated.

Cheers.

Mark.

Re: Will not run once hot.

PostPosted: Sun May 17, 2020 10:22 am
by TBG
My guess is the coil. They are miss-leading little tinkers and until I mounted mine in the cockpit I had many problems with the coil getting too hot and mis-behaving, although all seemed well at the time.