924Board.org

[AznDrgn]

For the first time in 10 years my '78 924 finally got to get on the roads. Overall I think the car was great, the ride was a bit more bumpy than I am used to but other than that it was pretty decent. I was amazed at the fuel efficiency I was running, did an 80 mile drive on the highway at about 65-70mph and I only ended up burning 2.5 gallons. Although most things went well I did have a few problems:

1.) Warm start problem- Doesn't seem to get enough gas to start up when it is warm. If I pop the hood and push the air sensor plate up a bit to get some fuel in it fires right up. I've checked out the WUR and it has the required 20 ohms of resistance, cold start valve works, temp sensor was just replaced and I know it is good, grounds are good, aux air valve is good.

2.) Alternator wasn't charging very well- At highway speeds the engine was reving about 3500rpm and the alternator was only charging at about 11V. The belt tension is as good as I can get it with the alternator bracket being on that rubber block. Maybe I need to look into changing that little piece of rubber with a hockey puck as mentioned in the FAQ.

3.) alternator/water pump belt cuts into my lower radiator hose. I got this hose from a local Trak Auto and I'm guessing that the hose was just measured wrong so I will be getting one from Porsche in a few days.

4.) Speedometer- Reads about 5-10MPH faster than the speed that I am actually doing. Is this the cable maybe missing gear teeth or maybe it has the wrong gear ratio somewhere along the line....

5. Odometer doesn't work- I'll be looking into the gears inside and the cable, any idea where I can get these?

6. Oil Pressure- Is there a rule of thumb to go by for RPM vs oil pressure? At highway speed I was doing 3500rpm in 4th and my oil pressure was at 2 bar, kind of low in my opinion. Running 10W-40, probably will change it soon to synthetic and then add an intercooler when I get time and money.

I just got back and thought I'd post what I had before I forgot it so if anyone has any suggestions on these problems please let me know. I know most of these answers are probably in the FAQ, if so just say FAQ and I'll go back and look again.


Thanks
Danny

[ltgland]

1.) Warm start problem-

mine does soemthing similar, and ideas? I suspect pressure in the fuel system

2.) Alternator wasn't charging very well-

Mine swings from 13v ro 12 and below when its wet. Check the alternator grounding, someone had a problem of low output until he ground it. And check other groundings, this is the only reason I can think of why mine drops when its wet (besides a leak over the fuse box!). Before you swap the alternator, it may be better swapping the voltage regulator. The alternator belt is the same one that runs the water pump, how is the cooling?

3.) alternator/water pump belt cuts into my lower radiator hose.

yip, wrong sized hose. I have the same problem with the alternator air hose.

5. Odometer doesn't work-

there is something in the faq about this, like the line on the wheel end or such like, its easier than removing the meter.

6. Oil Pressure-

it is low... I use 15w-40, but mine seems a bit too high.


later

[gohim]

#1 Warm Start. CIS fuel systems don't like being parked. On cars as old as yours, parked for long periods of time, fuel distributor probably has parts sticking. It's isn't unusual for cars to act yours, running on two, then three, then all four cylinders after running up the rpm. You could try running a high concentration of fuel system cleaner for consecutive tanks of gas to see if this improves. There is also the possibility that you have a blown head gasket, as this is also the way these engines run after sitting, and having coolant from a leaking headgasket short out one or more spark plugs. Running up the engine rpm blows the coolant off of the plugs and the engine runs on all four cylinders, until it is shut-off again.

#2 Low alternator charge rate. Go to the Porsche Dealer and get the latest alternator bushings. They were superceeded to a nylon/plastic over 10 years ago. The old rubber bushings didn't seem to last more than a year or two, before they crushed, and then the alternator lined up crooked, and would not tension properly. Another result of this problem is damaged alternator adjustment brackets.

Check the condition of the battery cable that runs from the battery to the alternator and the starter. Battery acid has a tendency to run down the cable and corrode the wires at the connection to the starter, which also affects the alternator since the wires from the alternator run to the starter.

You should also consider pulling the alternator, and having it tested for Free at a Kragen or AutoZone Store. The alternator could have low output because the brushes (which are part of the voltage regulator module), are worn-out. The voltage regulator is easily replaced, and relatively inexpensive. (about $30-$40).

#4 Low Oil Pressure. Oil Pressure should be about 1 Bar per 1K rpms. 4-4.5 Bar at 5K rpms. lower limit is about 1 bar at 1K rpm with a warm engine.

Low oil pressure could be due to a worn or damaged plastic elbow on the camshaft oil supply tube under the valve cover. If you did not replace this plastic elbow, before you started the car up, remove the valve cover, unbolt the oil supply tube, and check the holes to make sure they are clear, and replace the elbow.

You didn't mention replacing the oil. You aren't running the engine on oil that has been in it for over 10 years are you? The oil could be deteriorated, or diluted from gas, or coolant that has leaked into the oil after all that time. It would not be safe to run the engine on oil of unknown condition, and this could be the reason for your low pressure reading.

Synthetic oils are thinner than conventional oils. If you have any leaks, or low oil pressure, the problem/s will get worse, if you switch.

#5 Inaccurate Speedo. Porsche S
peedos are typically fairly accurate. Incorrect tire size could account for a inaccurate speedo readings. What size wheels and tires are on the car? There are no different sized gears for the 924, and missing teeth on a drive gear would create noise, and a higher error than you are reporting. What makes you think the speedo is wrong?

[ This Message was edited by: gohim on 2002-05-29 11:17 ]

[AznDrgn]

My warm start problem isn't just when I have left the car sitting for a while. I could stall out and the car won't start, or I could have stopped for 5 minutes and it'll do the same thing. As for a leaking head gasket I don't think there is any problem with that. I drove about 200miles this weekend and it was running fine, no water in the oil and the water level was the same as when I started.
As for the oil the elbow is fine I just checked it before I got the car on the road. The oil was changed a few months back when I got the car and it has only been run for maybe a total of an hour on my driveway.

[Mike77]

I had a similar warm start problem. I did 2 things that seemed to fix it. The first solution is to make sure your fuel injector lines are supported up above the engine with the little brackets. Mine weren't and it was vaporizing the fuel in the lines from the heat generated by touching the engine. That solved the big problem (not restarting even if it had stopped for a very short time). The second fix was to wire up the cold start button as described in the FAQ/tech section of this website. That fixed the problem of hard starting after 15 minutes shut off. Pushing that button if it won't start gives a shot of fuel and gets things going

[JvGinPDX]

Low oil pressure and voltage on the guages is often a result of a bad ground wire at the instruments. I run 15/50 dino oil in mine, and the pressure is better than 10/40 would give. Try this test. Rev your engine to 3000 rpm. keep it there while you turn on the lights, heater and wipers. if you indicated oil pressure drops, your guages are lying to you.

[endwrench]

I can't find my repair manual at the moment and am not completly familiar with the 924 CIS system yet but I did own a VW Rabbit once that had the same hard start problem. Turned out to be a bad fuel accumelator (sp?). I don't know if the Porsche uses one or not. They hold pressure on the system with a spring loaded diaphram. The diaphram ruptures then leaks back to the tank allowing vapor lock. Might be worth a look.

Todd

[ltgland]

there is one, it at the rar, near the fuel pump. I have a manual fuel pump override, which pressures the system if Im having problems.

[larso]