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Read it again, with special attention to vaporized fuel.
@technicalninja do you have a recommendation for a low-cost, in-line check valve?
DNM
Nope, every inline check valve I've tried has not worked very long and appears to be a restriction in the fuel line.
I haven't even looked for one for the last 15 years. Maybe someone has a good one now.
Replacing the fuel pump is the "normal" fix. With OEM fuel pumps the check valve usually lives for 10-15 years.
Aftermarket not so much...
Most modern car have a fuel pump prime feature where the pump runs for 5-10 seconds regardless of an attempt to start.
Chevy truck with a bad check valve I normally advise ignition to ON (you can hear the pump run if you listen) when it turns off ign to OFF for 15 seconds (lets the timer reset) back to ON 10 seconds, back to off 15 seconds, then an actual start attempt.
Usually starts instantly...
I do not recommend a $800 fuel pump job for just a bad check valve; I have to see another issue with the pump assembly before suggesting a fairly expensive job.
Now, any 20 year old car that I've blown I ALWAYS replace the stock ancient fuel pump anyways.
The stock Miata fuel pump has enough flow for the OP power level.
I just wouldn't use an OLD stock one.
The chances of a fuel pump failure taking out the engine are just too high...
That's why I asked "Have you changed your fuel pump?" in a previous post.
I don't think he's even checked fuel pressure yet.
I'd have done that first.
If the pumps new and exhibits loss of static fuel pressure at rest I'd probably build a momentary FP on switch. A button powered by a circuit that is only hot with ignition in on/start and requires being held down to function.
That might be a permanent solution.
It would work fine as long as the user was technically competent and understood what was going on.
My normal appliance car customer would not be a good candidate for this work around...
Modifying a fuel pump supply circuit also comes with increased liability for the shop that does this professionally (for money).
He'd have to be a friend of mine to have me do that for him.
One other thing that can take static FP down is an internally leaking fuel pressure regulator (return style systems only). Pinching a return line with a pair of needle nose vice grips is the usual "test" procedure.
ONLY pinch rubber lines. The hard plastic lines will split if you do this to them.
I certainly wish that I had replaced my pump with and OEM. I have spent that much on aftermarket. The aftermarket checks seem to work for about a month. I have a very long (2.1 second) Priming Pulse delay. This setting actually results in about a 4 second on time before the prime. When the pump stops, I move the key from "ON" to "START". This works well. When the aftermarket pumps were new, and with the original OEM pump, before it ran out of fuel at the top end; I used a 300mS delay and the car started well with turning the key directly to "START".
I have not monitored fuel pressure, but am going by how quickly the car actually fires off from turning to "START".
I was hoping I could return to a faster start by adding an in-line check, but suspected the ones available might be junk.
I have an idiot light connected that turns on for that 4 seconds, in case things are noisy and I cannot hear the pump. When the light goes out, I go from "ON" to "START". This way, the pump runs for 4 seconds, purging, then primes, then I crank. Just not quite as OEM as I'd like. I have noted that my Ford Expy delays cranking for about a second before actually cranking.
Here's a guy who made my push button prime circuit AUTOMATIC without any annoying buttons.
Totally "transparent" requiring no other user inputs beside patience...
You are still starting it like a diesel however.
Freaking Engineer...
My hat's off to you Sir.
Well Done!
And at this point someone HAS actually come up with a software solution to heat soak...
I was wrong...
A Kitten for you
I think it is likely a bug that allows The pump to keep on for more than the default 2 seconds, but it works. I stumbled across that. The timer / light idea was given to me by Matt of DIYAutotune.
The above doesn't cure the root cause of heat soak.
It looks like it is a very nice work around, however.
Another free test for the OP is to merely leave his hood open after heating it up.
If it starts fine, then he really does have a classic heat soak issue and the only true fix for it is to
Cool the engines...
10-10-2022, 11:01 AM
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