TheSamba.com :: View topic - '85 Cabriolet will not idle or restart once it is hot. Help!

Wed Apr 20, 2011 11:25 am

The other day my son's '85 Cabrio developed an annoying tendancy.
I replaced the radiator and upper radiator hose (lower one already new), and since then, it will start and idle/run fine when cold, but as soon as it gets warm (today I noticed that it happenend at exactly the same time as the cooling fan kicked on) it will begin to really hunt at idle, then will stall and refuse to restart until it has cooled some. Then once it warms up again, same thing happens.
Am I correct in thinking that the temp switch in the bottom of the radiator only turns on the fan? Or does it send a signal somewhere else, too?
(I actually swapped the fan switch out for another one, and it did the same thing)
I have already checked for vacuum leaks, but I don't really think that's it, as it starts, runs and idles fine when cold.
This car is pretty new to me, and I did fix several vacuum leaks, cleaned the CIS flapper, etc. to get it to idle when cold, but it has been running trouble free except for a seeping radiator for several hundred miles.
Coincidence that it happens when the fan comes on?
I will take a look at my Bentley, but it isn't here right now.
Any ideas?
Thanks in advance,
Greg
'85 Cabrio (first water cooled VW)
13 Air Cooleds

Fri Apr 22, 2011 10:55 am

I don't think that it is the cold start valve, as it stalls when it gets warm, then is hard to restart.
If the pulse on the 5th injector was bad, I could see the hot start problem, but not the idle hunting and stall
Also, can anyone reccomend a fuel pressure tester that is easily available that will work on this car, as well as other makes and models?
Thanks,
GB

Fri Apr 22, 2011 12:32 pm

The switch on the bottom of the radiator only works the cooling fan.

I'd still try pulling the cold start injector and make sure it's not sticking on - that can make for problems.

The fuel injection on this car, that's still the old style CIS - the warm-up (a.k.a. control pressure) regulator on the block affects the system the most on those. (and for simple hot-starting, the fuel pressure accumulator) Both of those have to be tested with a CIS fuel pressure test rig though.

The thing about fuel pressure testers on CIS fuel systems... you need three things - 1. All the correct size fittings. 2. Has to be a high pressure gauge (100PSI) 3. An inline shutoff valve. Combine all those together and that's why test kits usually start at like 90 dollars and up. Now, the gauge itself in those kits, I've simply unscrewed them from the test rig and then "screwed" them into a piece of hose and clamped it, and used that for the later Digifant lower pressure VW push-on test ports. Not sure how applicable that would be for other cars though. However, they do sell test rigs for other cars with "add on" kits for CIS, usualy both of those run the price up well over 100 bucks.

-Andy

Sat Apr 23, 2011 8:33 pm

I have ordered a fuel pump relay (long shot, I know) and a CIS pressure tester that I hope I'll be able to adapt to use on other things, as this will likely be my only CIS VW ever, as I am usually strictly an air cooled man.

Getting a little worse, as now even when cold it hesitates like it's running out of fuel sometimes when you shift. The warmer it gets, the worse it gets, til the guage gets just over halfway and it stalls and won't restart til it cools.
Bummer. It was running so good before.
GB

Thu Apr 28, 2011 3:25 pm

My jetta will do the same thing as well as my old '87 golf when it overheated. Did you change out or remove the thermostat, or replace the water pump.

I replaced my radiator, thermostat, and water pump on my Jetta and it still got hot. The fix for my Jetta was to remove the head, clean it real good and replace the head gasket. It runs real cool now.

I replaced my radiator, thermostat, and water pump on my '89 Golf and that fixed the problem.

It sounds like it is over heating.

Thu Apr 28, 2011 5:50 pm

The water pump is visibly a recent replacement, belts are tight, hoses are new, radiator is new, and the thermostat is new and of the correct temperature.
Fuel filter is new (@250 miles).
Plug wires and plugs are new.
I really don't think it is overheating, as the fan cycles properly and the temp gauge shows well within normal range, and the car just doesn't get that hot.
This problem just started one evening when my son was driving it. Driveability was not a problem before.
It wasn't the fuel pump relay (of course), and I'm still waiting on the fuel pressure tester that I ordered.

Thu Apr 28, 2011 5:53 pm

On your Jetta, did the gauge show that it was hot?
Also, what would actually cause it to run like that if it WAS overheating?
Thanks,
Greg

Fri Apr 29, 2011 7:40 am

Assuming that the thermostat is working properly and you are getting proper water flow, it is possible to have good water temperature and still over heat if the oil is low or not circulating properly.

I am having a problem with my car right now where I lose power but it still runs. I am beginning to think that it is related to the oil as well. I do not know much about the hydraulic lifters but I think the oil pump is not getting enough oil to the lifters and the valves are not opening properly, causing it to run bad. Does anyone know anything about hydraulic lifters?

Fri Apr 29, 2011 4:05 pm

You might be right about the overheating.
I had a little time to look at it this afternoon, and I took it for a drive.
I drove probably 15 miles or so, and all the while it ran great, no hesitation, no stalling, perfect. The temp gauge stayed at halfway or lower the entire time.
I brought it home and let it idle in the driveway for a while. The temp gauge slowly climbed, the fan cycled on and off (didn't seem to stay on long), and after about three fan cycles, with the gauge reading about 2/3 of the way (still a long ways from 'hot') it began to stumble and hesitate. I jumped in it in an attempt to get some airflow through the radiator to see if it would run better as it cooled, but it wouldn't run well enough to get far at all.
I'm thinking now that you could be right about the water pump. It's possible that it isn't flowing enough at idle to cool the engine, even though it looks newer. (I just got this car recently and I know nothing about it's history)
The radiator, hoses, belts, and thermostat are new (I installed them)
I'd like to hook up a real water temp gauge and see how hot it is really getting. If have time tomorrow I'll try to do this.
Is there a higher flow/better performing water pump available for this engine?
I can't remember which fan switch I have, but I remember that it is the most common one (85 C?).
what are the temp fan switches that are available?
Thanks for the help.
GB

Fri Apr 29, 2011 5:11 pm

There are 2 types of water pumps that I know of but I don't know the part numbers. I believe that one in German Bosch and the other is Japanese. All I know it that the good one has spiral cone prop fins like a turbo and the other one has prop fins that look like a flat plate of metal that has had the ends bent over. I am not an expert on this but I believe that the turbo looking one has better flow. They make some out of plastic too which I believe is more common now.

[/code]

Sat Apr 30, 2011 1:14 am

I've used both types and never noticed a single difference in how well they flow. Or at least, both style were more than adequate to cool the engine and the thermostat had no problems maintaining the temperature.
Instead of the style of impeller, I'd be more concerned if it was one of those "turbo" ones, but made out of plastic - I've seen it where those plastic ones come "unstuck" from where they are pressed on, and then some serious overheating can result. I won't use pumps with plastic impellers.
-Andy

Tue May 03, 2011 4:00 am

Fixed.
I replaced the water pump and installed a 180 degree thermostat, and while it didn't hurt anything, it didn't help either. The water pump impeller was worn, so it didn't hurt to replace it.
Also, someone had the countershaft pulley on backward, so I fixed that, too.
The fuel pressure tester showed up and I hooked it up.
Pressure started at about 60PSI, varying erraticaly between 50 and 60, and slowly dropping. The car ran OK until it began to dip into the lower 40s, and stalled at 38PSI.
It was the transfer pump.
When I pulled it, both rubber lines were pretty bad. Most of the return was missing, but the short rubber line between the pump and metal piping was probably pumping more fuel out the sides than was getting to the second pump.
The ground wire was unhooked when I pulled the pump, and the spade terminal was shot and wouldn't stay in place. I replaced it.
I didn't try the pump before I pulled it, so I'm not even sure if it was the ground or the fuel hose, but when I reinstalled it, I have a rock steady 72PSI now.
Car runs great, no matter how warm it gets.
Thanks for all the help,
Greg
13 Air Cooleds and one lonely Rabbit Cabrio.