'83 SC hot start problem

[LanceKTM950]

Greetings everyone!
I keep saying I'll make time to deal with this but since I'm on-call at work the time just doesn't happen so I'm asking for suggestions to get me started.
My '83 SC Cabrio is having a hot start problem. Starts immediately when cold, even if it sits for months. But drive 18 miles (my drive to town) and try to re-start within 3 hours and it's no go. Guessing it's fuel related, clogged filter (not too likely), fuel pump (works when cold), or accumulator or temp sensor. I can't afford to just swap parts but being in the wilds of Nevada I don't have a knowledgeable mind to pick locally, nor do I want to be stuck with a non-starting car if I have an ultimate failure. Could it be a relay?? It turns over fine but seems like no fuel, will try and ultimately catch if I floor the throttle and try starting for a minute or more (no more than 30 seconds at a time).
Just looking for a good starting point...
TIA,

Lance in Elko, NV

[boyt911sc]

Lance,

Check your fuel pressures (residual, control, and system). You need a pressure gauge kit to do the test. The residual pressure could be the problem. The three (3) most common culprits for residual pressure loss are:
1). Defective fuel accumulator.
2). Defective FP check valve.
3). Defective FD return line valve.

Tony

[mhackney]

Lance, it might seem like a PIA but what Tony is saying (and probably everyone who has gone down this path will agree) is dead on - find a fuel pressure gauge and measure! You can get the kit for cheap at Harbor Freight if you want to go the low cost route. There may even be a Pelican in your neck of the woods with a gauge. The more hard data you can get, the better diagnoses can be made. With a CIS Porsche, a fuel pressure gauge should be part of every owner's tool kit.

And, since I see you have a cab, consider registering on the 83 Cab Registry I run!

cheers,
Michael

[stlrj]

Even a warm engine without residual pressure should be able to start immediately if the thermo time switch is working properly to engage the cold start valve which is designed to work in a warm engine that has been without residual pressure for over 3 hours.

But to put your mind at ease about residual pressure, you could easily test it without gauges simply by reaching under and pushing up on the sensor plate while feeling for any resistance after 15 mins. If you feel any resistance, you have residual pressure... it's that simple. After 20 min to a half hour all residual pressure is gone and yet your engine should still be capable of starting instantly with the cold start valve, provided the thermal time switch is working.


Cheers,

Joe

[LanceKTM950]

Awesome suggestions guys. My fuel pressure test kit is buried somewhere from when we moved from IL to NV three years ago, I guess it's time to dig it out. It's been 20+years since I've worked on this type of fuel injection system and my memory about it is almost non-existent. Again, thanks for the tips, time to dig and then get dirty!
BTW, this baby has almost 200,000 miles on it!

Lance

[Bob Kontak]

Originally Posted by stlrj

But to put your mind at ease about residual pressure, you could easily test it without gauges simply by reaching under and pushing up on the sensor plate while feeling for any resistance after 15 mins. If you feel any resistance, you have residual pressure... it's that simple. After 20 min to a half hour all residual pressure is gone and yet your engine should still be capable of starting instantly with the cold start valve, provided the thermal time switch is working.

Joe, great info on lifting up on the sensor plate to feel for residual pressure.

I do not buy only twenty minutes to a half hour wait is fair in Nevada in the summer to refire the csv.

What is the temp cut-off on the csv? 115F-ish? In 30 mins your engine bay is going to cool down to under 115F in Nevada after a 20 mile drive?

Short term before gauges arrive, turn key on after two hours - when warm, lift sensor plate for three seconds and start car.

That is a slam dunk test for a warm pressure leak. It does not tell you where the leak is, though.

[stlrj]

Thermal/time switch is stamped 45 degrees C, but after a 20 min drive it would not need the CSV to get started anyway. Three hours later the CSV should be working to eliminate long cranking times.

[Mike in FL]

I had the same warm start issue with my 81 911SC - ended up being a defective fuel accumulator.

[Bob Kontak]

Originally Posted by stlrj

Thermal/time switch is stamped 45 degrees C, but after a 20 min drive it would not need the CSV to get started anyway.

Yes it would need the CSV if residual pressure was not held.