82 AT Starting Issues

[mikebloomfield]

I posted this over on the other board, and I hope its ok posting it here too.

I'm trying to track down a no-start issue. Here's what my car is doing, and a theory:

"Hot Start" (couple hours after driving it last): Car starts right up. No cranking.

"Warm Start" (next day or a couple days after driving it last): Car starts on first crank, but does crank a bit before starting. Not a lot to make me think it was abnormal, but after some research, I realize the car should always start the way it does at "hot start."

"Cold Start" (a week after starting): Car starts, but you have to crank it 4 or 5 times. Right before it starts, it stumbles and wants to catch but you have to crank it again. It feels like fuel starvation.

I'm thinking fuel pump check valve. This is an 82, so I don't know if its integrated with the fuel pump or not, but I can add it if it is, correct? I'm thinking over time, fuel is going back into the tank, and there isn't enough fuel in the cold start valve to get it going until the fuel pump works for a little while. Is there a way to test for this valve going bad? I originally thought this issue was electrical because a jump start got it started, but now I'm thinking that was coincidence, given that I put in a new battery.

Could it also be the thermotime switch?

Any opinions? I was thinking new fuel filter anyway, since I don't know when that was changed.

[MPDano]

Euro or US Model? You can tell if the check valve is on the Fuel Pump if the neck is very long.

I have an 81 Euro which is CIS.

[mikebloomfield]

This is a US 82, L-Jet.

Haven't taken anything apart yet, so excuse the dumb questions: The fuel filter is the larger silver cylinder closest to the camera, right? The fuel pump is behind it, with the check valve to the right.

Does my theory sound plausible?

[MPDano]

Originally Posted by mikebloomfield

This is a US 82, L-Jet.

Haven't taken anything apart yet, so excuse the dumb questions: The fuel filter is the larger silver cylinder closest to the camera, right? The fuel pump is behind it, with the check valve to the right.

Does my theory sound plausible?

Yes, your ID'ing parts is perfect. I would start with a new fuel filter. Also, take a pic of your fuel pump area. This will also identify if you have an in-tank pump.

"LEOS928" get prepped for Painting. Finally!!

[stepson]

Put a fuel rail pressure gauge on it and you would know immediately what is going on there. I honestly dunno if I would even mess with the fuel filter yet. I have never seen (although I have heard stories) a clogged fuel filter on any of my cars, but I suppose it's not out of the realm of possibility. More likely a bad check valve (and the fuel is just draining back into the tank and the system has to be repressurized before it starts) or leaky injector(s) which require the resultant flooding to be cleared out before it starts.

[MPDano]

...just a cheap troubleshooting part, where he may need to change anyways. Where is the Check Valve on a non-CIS? Pic?

[mikebloomfield]

Would leaky injectors be indicated by anything else? I should mention the car runs great, regardless of how it starts.

Also, if it was a flood condition, wouldn't that mean I would have to wait before it starts? I'm having somewhat of the opposite effect, the longer it goes between drives the harder it is to start.

I'm definately going to change the fuel filter and the check valve. I'm hoping my fuel filter doesn't have one internal, but I imagine I can add an external one.

Thanks for the replies!

[MPDano]

Originally Posted by mikebloomfield

I'm hoping my fuel filter doesn't have one internal, but I imagine I can add an external one.

!

Drop the back plate (two 10mm bolts) and take a pic. This will verify.

[aluminum]

"stepson"
Put a fuel rail pressure gauge on it and you would know immediately what is going on there.
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Let the gauge sit and watch it >
Yes the Injectors will leak down some > Normal
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Cold Start test : tap the starter just a click then off that will run the pump a bit / tap it again ( not turn it over just tap it )
this should prime the system and pressure up
Then try to see if it starts up normally .
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MP Dano is correct the Check Valve could be bad and draining back
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The cold start fast idle should be working when cold and should drop to normal after a few Min's
Let the Pressure Gauge sit over Night and see how much it drops .
New Injectors seals would be nice . Little O Rings > might want to do the Injectors when you have them out > Send them in for Cleaning and such .
Or you can just change the seals and run some cleaner through it >> However if you want good millage then send them in and change the fuel filter before starting it up ( I would Change it before I Evan remove the Injectors

[stepson]

Originally Posted by MPDano

...just a cheap troubleshooting part, where he may need to change anyways. Where is the Check Valve on a non-CIS? Pic?

AFAIK, it's in the same place (screwed into the end of the fuel pump). And yes, I agree, if you're going to be disconnecting any of the fuel pump/check valve/filter stuff, replace the filter then.

As far as leaky injector/flooding, I was thinking (probably erroneously) that the engine may need to get rid of the excess fuel in the cylinder before it actually cranked.

I don't think that '82 had internal pump-only the screen, but verify by checking for the two extra wires that follow the hose from the fuel pump to the tank. I don't think the symptoms you describe would be attributed to a clogged internal screen or filter.

If you do put a fuel rail gauge on, it will naturally leak down, but I can't remember the speed at which it is deemed excessive. IIRC, that exact thing is covered in the WSM.

And, as Aluminum describes bumping the key, you could also jumper the fuel pump before you attempt to start it, to pre-pressurize the fuel system. If it starts immediately, where it did not before, you would have a pretty good idea that it was the check valve.

[mikebloomfield]

Thanks for all the great replies. One of the reasons why I think its the check valve too is the cranking it for 4 or 5 times before it finally start acts to pressurize the system like aluminum's bumping the starter. I'll definately try jumpering.

Someone on the other board mentioned the cold start valve. It should kick in when coolant temp gets below 80 degrees or so, according to the WSM. But do the symptoms I describe sound like it? I would imagine that just cranking it wouldn't heat the coolant enough for the cold start valve to kick in.

I'd like to test this, I put a probe from my mulitmeter on each of the pins in the cold start valve, after unplugging, correct? WSM says 8 ohms is the correct reading.

[stepson]

It hasn't been below 80 here in so long, I wouldn't even know what that felt like.

[aluminum]

i think i will give you a job >> self pay > you can pay yourself what ever you want like $200 per hour like a real Porsche Shop
here is your fuse chart ( pass side foot well ) link :
Key
(1) clean all the fuses with a " Eraser " Yes a Eraser will clean them > remove and replace them very carefully or they will brake .
(2) very carefully remove the following relay's ( disconnect battery and slip a thin blade or screwdriver under each side of the relay and slowly rock it out back and forth ( if Its stuck most likely it is corroded with Green Gunk on the Posts and post slides ) if Corroded clean with starting fluid blow out with compressed air gun
(on the Chart ) Relay's # 7 start Relay / 8 Fuel Injection relay / 19 Fuel Pump relay
clean any relay's that show Green Corrosion coming out along the base .
A Small Brass Brush ToothBrush size is a big help
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don't forget to clean where the prongs plug in if Corroded > Starting Fluid then Blow Dry compressed air Gun .
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same way with the 14 pin connector Pass side fender well up toward the front next to the jump post
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Porsche's are a Electrical Nightmare and these are old style fuses that constantly degrade > like when your in your good clothes in the Parking area in Las vegas and you get in and no start hummm
Much better to just clean up the Fuse Panel once per year .
Let us know how you like your New Job and How much you decided to pay yourself $$ ??