No Hot Start

[Howard M]

This is not the typical "won't start hot" problem. This issue needs no heat soak. My 1976 911S stranded me at Lime Rock yesterday, the first time it has done so in 27 years. Long story short: starts immediately and runs fine when cold. After ten minutes of either driving or idle the engine will not restart, even if I try immediately (instantly) after the shutdown. It has plenty of battery and starter, but it will not ignite. If I try to start the car immediately after shutting it off, it will not start; but 45 minutes later it starts right up and runs perfectly until I shut it off. I suspect it is either the MSD/Pertronix or the fuel pump and I will do some diagnostics tomorrow. Any diagnostic recommendations or similar stories? Thanks.

[lfot]

I have had and am having a similar problem on my 82 CIS 911. Once it was the check valve next to the fuel pump. Fixed it and problem went away. Now it's doing it again. I believe it is the Fuel Accumulator. It starts to leak and the fuel loses pressure, allowing the fuel in the lines to vaporize with the heat. (so I'm told)

[sfoster13]

I had this happen to me twice. Each time it was the CDI box.

[Howard M]

That would be some leakdown in my case. From perfect running to no-start in two seconds. I'm going to clean my battery ground connection and the transmission ground strap tonight in preparation for tomorrow's diagnostics. I'm thinking that it must have something to do with the "start" position on the ignition switch, even though the starter ois operating perfectly. I bet the car would start fine with a "bump" start. Could the fuel pressure be ok to run but too low for a hot start?

[lfot]

Originally Posted by Howard M

Could the fuel pressure be ok to run but too low for a hot start?

If it's a CIS engine, the problem may be that if there is a lapse in pressure while the fuel pump isn't running, the overall pressure of the system will decrease and cause the fuel to turn to vapor in the fuel lines of the engine compartment (in hot conditions). So you sit there running the starter for a while until the pump builds the pressure in the fuel system back up. This pressure could lapse in a number of places.

If the car finally starts ok and runs, your fuel pump is probably ok.

I'm no expert though. This is just my speculation. I've just been dealing with these CIS warm-start pressure issues for a while.

[Howard M]

I don't think the engine will light up no matter how long I run the starter. Not so much as a sputter. Yet it runs perfectly from cold to hot as long as I don't try an immediate re-start. Although it sounds like spark I don't smell any gas. More data tomorrow.

[lfot]

But it will start and run fine when it cools off?

[Howard M]

The verdict is in. I did a cold engine fuel and spark check BEFORE I attempted to start the car this morning. I had both. The spark check was done per MSD recommendation by intermittantly grounding the white signal wire from the distributor. This had the advantage of removing the Pertronix system from the test.

Not surprisingly the car started instantly. After a brief ten minute warmup I shut off the car and immediately tried to restart it. No start. I rechecked the spark doing the same test I had performed ten minutes earlier. NO SPARK. I then checked the coil resistance per MSD's recommendations and got different numbers than they said to expect, but no wild numbers and no opens. I also checked the switched 12 volts, unswitched 12 volts and ground and everything was there...except the spark. It must be the MSD box, but I will send both the box and Blaster coil to MSD for checkout and repair.

One more test I plan to run is to skip the ten minute warmup, which hardly warms anything. After the expected cold engine start I will immediately shut off the engine and see if it restarts. I'm pretty disappointed in the MSD box. I have been a proponent of it for years; now maybe not so much.

[ERN911]

Howard just reading, it sounds like what I went through and it ended it up being my CDI box, how was Lime rock, did you make any subies flip LOL.

Ernie

[Howard M]

The only crazy thing about this, Ernie, is that the car starts when it is cold and runs fine for as long (or as short) as I don't shut it down. After that, forgetaboutit. I hope MSD can troubleshoot and repair it. It goes out to them tomorrow.

The Grand Am race was fun and the day was beautiful....until the gas stop!

Zone 1 is August 28 and 29. Stay home if you want to avoid an a$$ whupping.

[ERN911]

let me tell you, first you need to get your car running you only have 2 months, second I dont know whos going to be giving the a$$ whupping you're talking about, this past weekend at our Zone 12 Zone-fest my buddy Al took FTD in his 73T {Look out Parade goer's} he only beat me by .4 tenths him on his new Hoosier's A6, me on new BFG R1, the hoosier's are faster but I will give up the .4 to have tires last me almost 2 season's. Anyways it was a fun weekend and the people there where questioning if my car was stock they could believe the times we were running, I would love to be able to make it to your Zone Autocross and bring that trophy to south Florida but for now I will only concentrate on the parade one.

Ernie

[Howard M]

FINAL DISPOSITION: MSD found the returned unit to be defective. They "replaced unstable capacitors and updated the transistors". Meanwhile I bought and installed a new MSD 6AL and the car is again working perfectly. The repaired unit will be carried with me from now on as a backup.

[dshepp806]

Amen!!!!!!!!!!!

Doyle