I have spent the past several hours going thru the threads on CHT Rich / Lean and Hot Start issues from my search on "Hot Start". I am very impressed with the depth of knowledge and research you guys provided. THANK YOU!!!

My situation results from my first long drive in Minerva's 914 post restoration. There have been several short "test" drives without any noticeable issues, however Sunday evening I drove about 30 miles, at night, with air temperatures in the high 60's. Everything seemed to be wonderful, plenty of power and torque, no noticeable issues, other than one and only one time when I experienced a slight lugging or surging of the engine at just under 3,000 RPMs and I reactively downshifted and thought nothing of it. That being said, maybe there is nothing to this but I want to share everything I can remember about that evening, just in case there might be a fuel pressure issue at fault. When I returned home, I was backing it in the garage slowly since it doesn't have the rearview mirror installed yet, nor did it ever have a righthand mirror when the rear tires bumped up against the rain guard rise going into the garage and stopped. As I engaged the clutch I stalled the engine. I switched off the ignition and back on but the engine spun but did not fired at all. I switched it back off and tried again without success. I turn the ignition off and waited a couple minutes and tried again. Nothing. It had all of the sounds and lack of firing as if it had vapor locked as it did years ago before I relocated the fuel pump to the front. The next day and every time since it starts immediately and runs perfectly. I have not yet taken it back out for a long drive.

FAT Performance in CA built the engine with slightly oversized jugs and I remember them saying that I may have to increase the fuel pressure to work with the new engine but I didn't go into any more details about that at that time. I plan to call them tomorrow and ask if that might be something I want to address, even if it doesn't have anything to do with this issue. I'll also call John at Black Forest for his input.

So, I'm thinking that this weekend I should check the fuel pressure, check the CHT sensor and confirm all of the state of tune.

Can you guys suggest anything else or contribute opinions / thoughts on this? The fact that it was a relatively cool evening and the engine did not have time to change temperature relative to the sensor does not seem to be all that similar to the issues others have written about here.

Opinions PLEASE. And thank you in advance.

Distributor advance plates stuck at full advance when hot. Cools down and they loosen up and go back to no advance. Worth checking and cleaning.
Anytime it's a hot start issue it's three things.

Temp sensor malfunction
Fuel pump heat issues
Distributor heat issues

Lastly, and hardest to diagnose is the fuel injection wiring harness.

Perfect! Thanks, I'll start going thru the possibilities this weekend and report back my findings for the 914 memory hole. Good news is, this means I need to test drive her car, a lot. He he he!

Slightly larger pistons?
Please be more specific.

If you are running the stock fuel injection, you need to search for how to re calibrate your MPS to deliver the new required amount of fuel. Increasing the fuel pressure won't do it, FAT is wrong there.
a few guys here offer the service to re calibrate your MPS to match your needs....find them.

If you run too lean, the motor will be really hot and burn up the valves and worse. you need to get some gauges to see what is up with your setup.

Too little fuel ==== to much heat
too much advance on timing ==== too much heat.

Heat will kill the motor.

rich

Makes perfect sense! The motor seemed to me to be too lean to start and not too rich, as it would be if the sensor was the issue. I called FAT but they are closed on Fridays but I have their receipt boxed up with my paper work (we're in the process of moving) and I'll try to find it this weekend and call FAT again on Monday. Btw, it's been almost 3 years since they finished the engine and due to the local "In By Noon, Out By June" shop falling down on the install I'm sure FAT would have said "adjust the MPS to match" and not as I remember "adjust the fuel pressure". Once I get the correct info, I'll talk to John at Black Forest Racing to see if he can properly map my set-up. THANK YOU!!!

If BFR has a dyno, have them tune the MPS with the car on the dyno...its the best way to do it.
They have all the gauges.
It. would help them to know the exact motor specs, but they can do it without them if you cannot figure it out...the dyno and an AFR up the tailpipe will do the trick.

Rich

if its really a big jugged motor, the system will support 2.4 liter, but we will need to find you a different MPS from a VW 411 to do it.

rich

Should be able to get the exact specs on Monday. Thanks again, owe you several beers.

Talked with FAT Performance today, the motor retained the 7.9:1, so normal stroke and is at 2,055cc. Basically about an 80cc increase. They again suggested that a small boast in fuel pressure would probably help, but they also admitted that they don't normally stay with the factory FI on their motor builds, so do not have a huge amount of experience it but repeated that a small increase in FP and adjusting the mixture on the brain box should be all that is needed.

What'cha think guys?

What camshaft did they put in? One for carbs or stock?

Stock

Okay, finally had time to do some testing and the solution revealed itself straight away and it was so simple I'm kicking myself for not realizing it immediately.

First step is always to check the state of tune. I almost skipped over this as it had just come off the service bay after setting up the FI. I didn't want to allow the engine to sit at idle to warm up nor revved with no load since it has less than 25 miles on the rebuild, so I drove it around the neighborhood until warm. A block from my garage I stop at a stoplight and the RPMs dropped and it almost stalled, I kept the revs up remembering that it had stalled before and would not restart and I didn't want that to happen there. So I make it back, pull into the garage all the while blipping the throttle to keep it running. I noted that it was running very smoothly, it just wanted to choke and die at idle. Once I was parked, I slowly lowered to idle. Idle turned out to be about 400 RPMs and very close to stalling. I jumped out, popped open the cover, grabbed my long screw driver and brought the idle up to 800 RPMs and it smoothed out and purred.

That was IT! The cold start air bypass was feeding the engine air when it was cold and once it was warmed up, the valve closed and the car was starved for air at operating temp. When it died the first time I had the engine at operating temperature I didn't stop along the way so never noticed the idle issue until I stalled it backing into the garage and then it would not restart until the next day when it was cold again, so of course imagined the worse.

Now it starts first time, every time with no more issues.

What a dummy!

p.s. I almost didn't post this solution but thought I'd own up to being a bit s-l-o-w on this one

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