924Board.org

[Brians924]

Pardon me if this is redundant!

only issue when I purchased this car was the guy stated...

if you drive it 10 minutes here and there it will start everytime. but if you drive for an hour or more and stop the car, it will nt start unless it sits for hours.

just got it home and guess what? it didn't start. acts like it shuts the fuel off becuase it turns over just doesnt pop.

i read somewhere of a hot start relay bypass button you can do?

again, sorry if this is redundant.

Brian
_________________
1977 Porsche 924 n/a
2.0 4sp. w/59k

[staticsan]

Sounds like the WUR needs replacing. However, most people would recommend a fuel pressure test to be sure.

Also, have you tried holding the accelarator to the floor when you start it hot? That is what Porsche said to do in the actual 924 instruction manual.

Wade.
_________________
'82 British NA - Which I think I've been very lucky with!

[Brians924]

thanks for your reply!

I have tried the pedal to the floor and to no avail.

went out after 2 hours and she fired right up. runs great, and doesn't run hot.

the fuel lines and fuel pump(s) have been replaced.

Is there somewhere here on this forum that shows pics and location of this WUR unit?

Brian
_________________
1977 Porsche 924 n/a
2.0 4sp. w/59k

[Paul]

Welcome to the board and 924s! Nice car!

This is an age old problem with our cars and much info can be found by searching this board.

The problem is caused when the fuel pressure leaks down too fast after shutdown. This allows the under hood heat to vaporize the fuel in the lines under the hood. A fuel accumulator and check valves are used to maintain this pressure for a stated time (see factory shop manual). To combat under hood heat the radiator fan runs at a reduced speed for a few minutes after shutdown.

The key to starting the car is to clear the system of air and fill the fuel injection lines with some cool gasoline from the tank.
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

[Brians924]

Paul,
thanks for your reply!

I have searched the forums but I get so many unrelated results its overwhelming.

Your explaination is awesome, If this is the case... I should be able to pop my hood when I get to destination and shut car off, wait and if car starts then that's it.

sounds like it is time to search out the ins and outs of the fuel accumulator and check valves!

so, question is how to clear (purge the system) ?

thanks again,

Brian
_________________
1977 Porsche 924 n/a
2.0 4sp. w/59k

[Paul]

Since the fuel injection system is a bypass system, fuel is pumped from the tank to the fuel injection distributor. Unneeded fuel is returned to the tank.

So the key is to get the fuel pump to run long enough to clear the lines.

Some cars respond nicely to turning the key to run (not cranking), letting the fuel pump run until it stops, turn key off. Repeat a couple of times.
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

[staticsan]

If you sort out the loss of pressure, then you won't need to purge the lines.

The WUR is bolted onto the rear of the inlet manifold, below and behind the auxillary air valve and more-or-less between the cold start valve on the back of the throttle body and the distributor. It has two fuel lines and an electric connector. (It should be said I replaced mine because my symptoms matched exactly the problem a faulty WUR provides - and I don't have warm start problems anymore).

The fuel accumulator is underneath the fuel tank at the rear of the car.

Learning how the CIS works is recommended. The Haynes book has a good enough summary for most purposes, though I'm told it is a little incomplete for some cases.

Wade.
_________________
'82 British NA - Which I think I've been very lucky with!

[!tom]

Purging the system like Paul describes won't work on the '77 model year, as the fuel pump won't prime like described. That only happens in the later model years.

As stated, this issue is commonly caused by the system unable to maintain pressure after being shut down.

The following components are likely culprits that can leak if worn out or dirty (in no particular order):
1) Fuel injector(s)
2) Accumulator
3) Check valve

Any number of other components could potentially develop a leak which would result in the same symptoms.

There are numerous threads on the site that describe the process. Basically, step 1 is to perform a leakdown pressure test to verify that this is indeed the cause, then the troubleshooting to determine where the leak is (if there is indeed one).

I did a search for you. It discusses the late model design that Paul was referring to, so there are some differences between it and your car.

9XX girl had a great idea she implemented to get around the problem, but, again, this doesn't address the root cause.
_________________
78 924 NA
5-lug

[Ozzie]

4) the pressure regulator in the CIS can also leak down to tank.
_________________
Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

[Brians924]

thank you all for your much needed information!

It is time for some reading and investigating until the lil gremlin is found

onward!

p.s.

i did find that even driving for 10 minutes and shutting it off creates the no start symptom.

I will update here as I go...

thanks again
Brian
_________________
1977 Porsche 924 n/a
2.0 4sp. w/59k

[Ozzie]

for it to happen that quick I would suspect the accumulators.
_________________
Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

[Brians924]

Drove home 6 miles in 30 degree cold. Parked it, tried starting and she started 5 times in a row no problem. Funny!
gonna start going thru the tests and narrow it down tonight. Hopefully... lol

B.
_________________
1977 Porsche 924 n/a
2.0 4sp. w/59k

[Brians924]

ok took her out tonight, not as cold around 40 degrees F.

got home and she started no issues...

here are some photos i took.

the hot fix sayin the red wire with the white line etc... against firewall, is this the exposed wires?




2nd is what am i lookin at?





the third set 2 pics are of the underside of the tank, i was hoping to see the $120+ accumulator, but instead I see this?





please advise a noob! My Hanes book will not be in til end of next week.

if it is any conciliation, the engine bay is clean as heck eh!



help a fellow man woo his wifey with car!!!!

B.
_________________
1977 Porsche 924 n/a
2.0 4sp. w/59k

[!tom]

The hot "fix" you're referring to (more of a workaround, as it doesn't fix the cause of the problem) applies external power to the CSV.

The CSV is the fuel injector on your intake manifold.

Your CSV is in your 3rd picture. It's the thing with the blue connector on it in the foreground. The subject of the 3rd picture appears to be your heater valve.

Your accumulator is in front of your fuel tank. You have a picture of the bottom of your fuel tank. To see it, you have to be looking straight up along the front of the fuel tank.
_________________
78 924 NA
5-lug

[Brians924]

Is this the replacement WUR? And if so is the price right...

http://pages.ebay.com/motors/link/?nav=item.view&id=360444935759

Im thinkin if original it maybe best to change it, ill do the screw test tonight on the acumulator.

Brian
_________________
1977 Porsche 924 n/a
2.0 4sp. w/59k