Starting a 1979 with 5 speed manual

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07 Jul 2011 10:25 #5457 by EWM
My recently acquired 1979 928 has the following starting symptoms:

Unless started within the last few hours, the car will not start on the first crank. On the second crank, the engine barley catches on a few cylinders and then builds up rpms to around 1500 over about 5 seconds. During the next 20 seconds, the rpms drop down to around 900 rpms. After a few seconds at 900 rpm, the idle is smooth and the car will drive away easily.

My first guess was a fule check valve but this car does not have one. Befoe I buy more parts, does anyone have a suggestion on what could cause these symptoms?

Thanks,
ewm

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07 Jul 2011 14:22 #5458 by 928mac
Is the fuel filter clean/new?

Try cycling the key to on, wait a few seconds, then off, repeat and cycle key on again, do it a 3rd time and then try starting and see it it is any different. If it is better then it is fuel related.

My car dose not have a fuel check ball to my knowledge and if it dose it dose not hold pressure bast 10-15 seconds of turning the key off.

Maybe it is dirty injectors? is there a way for you to connect a fuel pressure gauge into the line for testing purposes?

Brad

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08 Jul 2011 22:26 #5478 by EWM
Thanks for the response.

The fuel filter is new. The injectors may be dirty but the cars runs extremely well once started.

Does anyone use injector cleaner additives in the early 928s?

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09 Jul 2011 23:01 #5482 by 928mac
Some may use cleaner.
I just ordered a set for $165

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10 Jul 2011 08:11 #5483 by srshaw3
My first quick (unrefined) thought is that a ;79 would be a CIS system, and have an additional cold start injector that connects to the top front of the plenum. At least that is my recollection for how my '80 Euro S was setup.

So, if your problem is at start up, perhaps that "extra" injector is not functioning properly and not providing the extra fuel the car requires when cold.

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10 Jul 2011 11:28 #5486 by Kiln_Red

My first quick (unrefined) thought is that a ;79 would be a CIS system, and have an additional cold start injector that connects to the top front of the plenum. At least that is my recollection for how my '80 Euro S was setup.

So, if your problem is at start up, perhaps that "extra" injector is not functioning properly and not providing the extra fuel the car requires when cold.


Yes, hard starting on CIS cars is very often the fault of the cold start injector. It's the first place to look.

Do you have a copy of the 928 Workshop Manuals?

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11 Jul 2011 07:24 #5503 by EWM
Yes, 4 binders came with the car. So fa,r forums and internet postings have far exceeded the manuals.

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15 Jul 2011 15:45 #5607 by EWM
Found a 3/8 inch or metric equivalent vacuum hose with a split. A new hose has helped the starting quite a bit. Starts on the first crank now but still requires slightly more grinding than I would prefer. The chase is still on.

The hose comes off a "T" on the right fender and goes to a part near the front of the engine on the intake manifold. The vacuum line with the "T" is above the air conditioner lines, and the split happened where the vacuum hose lays on top of a metal coolant line that runs parallel with the right cylinder head.

What I need is a picture or drawing with arrows and names of all external componets under the hood.

ewm
79 MY

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21 Jul 2011 20:52 #5669 by WyattsRide
Is this something you're looking for? It's for an 87 but it may help a little.

members.rennlist.com/v1uhoh/underthe.htm

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21 Jul 2011 21:15 #5670 by Kiln_Red

Found a 3/8 inch or metric equivalent vacuum hose with a split. A new hose has helped the starting quite a bit. Starts on the first crank now but still requires slightly more grinding than I would prefer. The chase is still on.

The hose comes off a "T" on the right fender and goes to a part near the front of the engine on the intake manifold. The vacuum line with the "T" is above the air conditioner lines, and the split happened where the vacuum hose lays on top of a metal coolant line that runs parallel with the right cylinder head.

What I need is a picture or drawing with arrows and names of all external componets under the hood.

ewm
79 MY


You need to stop now and totally refresh your intake vacuum hoses and connectors. All of them. These cars are old. One split hose will shortly turn to five. Also, you said resolving the issue with the first split hose helped the car to run better. Refreshing your intake will most likely cure all of your hard starting issues as it sounds obviously vacuum related now. It's an easy job and will pay off largely.

There is a vacuum diagram in the WSM.

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