924Board.org

[Hotrod2go]

Hi All,

Have a problem with the 1980 924.... and hoping for some help. It won't start in the morning but will in the afternoon. Can't figure it!!! Temperature variation? Timing? I give!!!!!??? Temperatures here in AZ are running around 80 degs in the morning and 100 degs in the late afternoon.

Can someone point in the right direction?

Also, is there a trick to keeping the exhaust manifold from leaking? Replaced bolts, lockwashers and gaskets, (along with 2 stripped hole helicoils), 3 months agao and now it leaks again and at least one hole seems to be stripped out again.

Thanks in advance!!!!!!!! -Phil
_________________
"Get In, Sit Down, Hold On AND SHUTUP!"

[Chrenan]

I would suggest 2 possibilities.

My guess would be that overnight you are losing fuel pressure, but since the car has been run in the morning, there is enough remaining fuel pressure for it to start in the afternoon. Fuel pressure loss could be from leaking injectors, faulty accumulator, faulty check valve, or some other leak in the fuel system.

Another possibility could be ambient temperature. If it is noticeably colder in your region in the morning than in the afternoon, the car may require the assistance of the cold start valve to get started. A faulty cold start valve could be your issue.

Anyway, hope that helps a bit, if something doesn't make sense, let me know and I'll try to go into more detail...
_________________
1987 951 - M193 Version for Japan

[Hotrod2go]

Thanks,

Could you suggest the most efficient and logical way to start testing these possibilities? The car has never started well after sitting... I wonder if the cold start valve would be a good place to start???

Thanks, Phil
_________________
"Get In, Sit Down, Hold On AND SHUTUP!"

[Chrenan]

Tests for the injectors and cold start valve are well explained in the Haynes manual. Haynes is available for cheap and is a must have if you don't already have it. Some book stores wil be able to order it in for you, some automotive stores may have it in stock. If you have trouble finding it, you can get it online from Chapters in Canada or Amazon in the US depending on your location (you should add your location to your profile, it's always nice to know where people are from).

Links for Haynes manual:

http://www.amazon.com/exec/obidos/tg/detail/-/185010073X/qid=1084906878/sr=8-1/ref=sr_8_xs_ap_i1_xgl14/002-9889842-7788843?v=glance&s=books&n=507846

http://www.chapters.indigo.ca/item.asp?N=35&R=383730&act=A03&Item=978185010073&Section=books&Catalog=Books&Lang=en&mscssid=G9SMXCA53JR78G2GMG29J6LNKA0V15H6&WSID=150552ADA0B97275411BB4D790580A1984F60118

The tests are pretty simple to run, and should help you find your problem. I don't know all the steps well enough to recite them here, so you may be better off picking up the manual. Plus, the pictures in Haynes always help to explain things.
_________________
1987 951 - M193 Version for Japan

[CMXXXI]

Ditto on getting a copy of Haynes. Someone on Board may have an extra copy for sale. There are copies all the time up for grabs - cheap - on E-Bay.

- Starting problem - hmmm, 80 in the morning and 100 in the afternoon - That's an awfully hot "cold start" as far as ambient temps are concerned. Who can tell us about the temps involved with the cold start system? The fifth injector seems to get a lot of blame, but I can't really recall anyone coming back and saying definitively that it has ever been the actual cause of their problems. I'd start with testing the thermo-time switch if you tend to think it's electrically related, and I'd start with a pressure leak test if you think it's fuel related. Sounds like a good opportunity to purchase that CIS test set you've been lusting after.

The specs for the control pressure regulator are almost "coincidental" in your case. The operational "band" for 80 & 100 just miss overlapping. (the minimum pressure @100* is just about the max pressure @80*). Might the WUR be going south, but still functional enough to work at high ambient temps? Here's the spec page:
(click for larger)

As for the exhaust manifold, it should be secured with studs and locking nuts, not bolts. I'm sure there is an engineering answer to why some applications use a bolt instead of a stud and nut (or vice versa), but I don't know the rationale. Often there are clearance and tolerance issues, but that may be beside the point for this discussion.
_________________
'79 Eurospec 931

[Hotrod2go]

Thanks! I have a manual and will get more into it tonite. Will post if I figure out something in the AM....

-Phil
_________________
"Get In, Sit Down, Hold On AND SHUTUP!"

[geddes66]

Here is my super cheapo test. get an extra 2 prong fuel injection system plug, hook it to the cold start injector and then using a couple of test wires (with clips) or some speaker wire rig a way to manually energize the cold start injector. energize it for a few seconds just before or while cranking it. If it starts in the morning then it will probably be the thermo time switch. Mine had the same problem and due to job problems my "test" system has been in use to start it for 4 months now.
_________________
The Porsche is now my son's, my car is cooler, slower but cooler.

[Hotrod2go]

Well, it looks like the distributor slipped, although it seemed tight and was at 25 degs!!! I reset it and it started fine this morning. Now I just have to fix that pesky exhaust manifold leak! Thanks again to you all for the help.
_________________
"Get In, Sit Down, Hold On AND SHUTUP!"

[Hotrod2go]

Well, I drove the car to work today and the gremlins bit.........hard.

Looks like another injector bit the dust. Runs poorly and max speed is 60... with a tailwind.

shook so bad the last 3 miles to work that the bolts loosened up again on the exhaust manifold and it leaks badly now. Going to bum a ride home from work and tow it tomorrow. Anyone want to take over??? I think I am going to retire from working on it. I will give someone a great deal on it....

1980 924 with sunroof and PW. I have several parts I have yet to have a chance to install...such as new struts, power antenna, etc.


Thanks for all your help guys... just tired and old!

-Phil in Arizona
_________________
"Get In, Sit Down, Hold On AND SHUTUP!"

[gohim]

Sounds to me like you are overtorquing the exhaust manifold nuts when you install them. Properly installed Helicoils don't strip out with a good reason.

You need to remember that the head is made of aluminum, If you overtighten the nuts, all you are going to do is pull the threads out of the head, or when the engine warms up, the threads will get pulled out of the head.

You could also be using the wrong torque spec. What are you tightening the exhaust nuts to? You are not driving the exhaust studs in tight are you? They should be only be screwed in finger tight.

As for the engine not starting when it is cold (in the morning, right?), this could be due to a head gasket leak (shorting out the spark plugs), or a leaking fuel injector. Have you pulled the injectors to see if they have a good pattern, and don't leak? Have you tried checking the residue fuel system pressure? Maybe you have a leaking fuel accumulator?

[Chrenan]

Don't give up yet...
_________________
1987 951 - M193 Version for Japan

[78porsche924]

i actually had a similiar problem. ran like crap when colder out, and then better when it was hot out. one thing you should check and it is cheap to do, reseal the fuel injector bushings. they only leaked when the engine was cool, but not when hot. another thing you should check is take out the fuel injectors and soak them in carb soak(got it from napa). Not sure if the injectors in the 80 were all metal like they were in the one i had, but if they are i would recommend soaking them in the carb soak for about 5-10 min, then rinse them in acetone or mineral spirits. if it turns redish and you see little red flakes, then you could be dealing with some rust. also works nice if your injectors are clogged up. also take out the fuel filter and look at the fuel coming out of it, if it is redish, then you might have a rusty tank. my fuel filter would clog up, then after a few hours it would slowly unclog from sitting and then run for a little bit before choking out again. the longer i let it sit before driving it, the longer it ran. hope that helps.
_________________
90 944 S2
78 924 NA <---now sold and killed by new owner
snailshell trans
Bae turbo kit
to check out my 944 S2 http://www.cardomain.com/member_pages/view_page.pl?page_id=388139

[Hotrod2go]

Okay, When I got the car there was only one stud in the head for the exhaust manifold and (2) holes helicoiled, which is why the head was off the car. I replaced the bolts that came with it using grade 8 bolts and lockwashers. I used the torque in the Haynes manual...and new gaskets. with the head off the car. I retightened these on the car after a month or so. At that time I found that one hole was stripped. I figure weak from previous owners and finally gave it up. BTW, I used locktite and put it in snug as there were no other problems, and........ it is one of the bolts that DID NOT fall out!!! Go figure! The remaining stud has broken off, I assume after the other bolts let loose. Car was running good yesterday morning until a few miles from work. Sputtered like the last time I had to replace an injector. My main thing is I don't want to have to pull the head for another helicoil repair.... If I can fix it without pulling then fine.

I will scope it out more this weekend if I get a chance. I have a 2-day class. Thanks for the input!!!

-Phil
_________________
"Get In, Sit Down, Hold On AND SHUTUP!"

[Hotrod2go]

I haven't found which injector is a problem yet, but was wondering if the head has to come off to drop the stock exhaust manifold??? Maybe I won't have to completely remove it but just in case... Is a header a better option?

Thanks!!!!!!!!!

-Phil
_________________
"Get In, Sit Down, Hold On AND SHUTUP!"

[Hotrod2go]

Pulled the spark plugs and all seem to be burning about the same. I thought one may give me an indicator as to which injector is bad, but I am set up to do the Haynes test now. Hey, where is the best/least expensive place to get some plug wires? Thought I would replace them while it is apart....

Thanks........Phil in AZ............anyone want to help???
_________________
"Get In, Sit Down, Hold On AND SHUTUP!"