dr bob

Greg, that's EXACTLY what the cooler is for. It keeps the fuel in the tank from getting too warm, and expanding too much (same as 'vaporizing') in the pump suction, as well as helping with boiling in the lines in the engine bay. On my 'other' CIS cars, keeping the tank close to full made sure the pump maintained prime. Ultimately the higher capacity pump was installed too. In the Saab 900 CIS car, for instance, the main pump is mounted inside the tank from the top, supposedly cooled (and quieted) by the fuel in the tank. Porsche installs the main pump outside the tank for cooling purposes (?), but adds the in-tank primer pump to help avoid vapor in the main pump inlet. If the victims listen to the pump buzz, I'll speculate that it speeds up noticeably when the system is vapor locked.

James Bailey

Thinking about it a bit more the 82-83 Euro CIS cars have an added solenoid valve and return line on the control pressure line running back to the fuel distributor. Perhaps it is the control pressure which gets screwed up and shuts down the injection. I always thought that was for hot restarts if the fuel in the line were to boil since it only appears on later Euro CIS I am not that familiar with it ..

Dennis Wilson

Jim,

The solenoid is called a frequency valve that minutely adjusts the control pressure based upon the input of the O2 sensor. It is doubful the amount of fuel it returns would have much impact on vapor locking. If it gets screwed up or a bad signal it defaults to a richer mixture.

Dennis

dr bob

Keeerect! That solenoid is modulated (with a PWM signal actually) based on oxy sensor reading to fine-tune CO (mixture). If you happen to have a fairly fresh sensor and a clean fuel system, you can 'tune' the screw on the metering unit to get the duty cycle on the solenoid at 50%, and be somewhat confident that you have the mixture correct. There are some dwell meters that offer duty-cycle readings. I just hook up the o'scope.

PorKen

I think Jim may be talking about the warm start valve. (1-4 side, roughly under the front of the airbox.)


The fuel cooler is more for reducing emissions from gas vapors?

bronto

When did the fuel cooler get added (or was it always there)? The vegas guys talked like mine had it, but he might not have known about older models.

KLVA

I guess that makes me a crazy person !! You are right, it is a swamp here in the summer but the guys in Baton Rouge don't even blink back a bead of sweat when visiting D.C. in August. I hope Kary gets that job and finds a way to make a reasonable commute...I suggest a new Camry for that purpose though and save the Euro for fun runs, DE at Summit Point and Frenzy in Oct !! Come on out early Sunday mornings heading up to Skyline Drive and that is where you would see me...usually back by noon before it gets too hot and humid !! Bon Chance, Kevin

kary4th

Well, it was hotter today than yesterday. After adding insulation around the fuel lines in the engine compartment, I had no problems.

If I get that job, I'll be adding another (or a different) fuel pump, no two ways about it.

You're right about something else for commuting, Kevin. It's just wrong to treat a 928 like that.

Thanks, all.

I'll let you know what happens.

bronto

More vapor lock reports.

I am finishing the last legs of my CA-UT-NV-CA trip. Yesterday was Reno to Fresno via Yosemite. Yes, serious vapor lock in warm (not hot) weather at the Tioga Pass entrance to Yosemite (10k feet elevation). There was a fairly long line at the entrance, and it is an uphill approach to the guard gate. As it became bumper to bumper, it started to vapor lock. I was able to restart it a few times before it became unstartable. I managed to get it off the road so it could cool off. At that point the needle was well below top bar, and cooler than it was in Vegas, but I presume the altitude was the main culprit. After about 1/2 hour it was good to go again, and I just kept the rpms high so fuel would keep flowing until I got past the entrance. I had occasional trivial issues until I was out of the park and at Oakhurst (2200 feet elevation).

I have questions for dealing with this. I live in a moderate climate but take frequent trips to very hot or very high locations.

* Is the wiring for the in-tank pump present in my '79? Is it a special pump or a second just like the external one?

* When did the fuel cooler get added? I am presuming mine doesn't have it.

* Black Sheep Automotive in Vegas advised me that I should leave the key on for 30 seconds or so before trying to restart in order to push cool fuel from the tank into the lines. But when I do that I don't hear the fuel pump running; does my '79 power the pump only when the engine is running or trying to start?

* Can someone supply me photos of where/how to insulate the fuel lines?

bronto

More vapor lock reports.

I am finishing the last legs of my CA-UT-NV-CA trip. Yesterday was Reno to Fresno via Yosemite. Yes, serious vapor lock in warm (not hot) weather at the Tioga Pass entrance to Yosemite (10k feet elevation). There was a fairly long line at the entrance, and it is an uphill approach to the guard gate. As it became bumper to bumper, it started to vapor lock. I was able to restart it a few times before it became unstartable. I managed to get it off the road so it could cool off. At that point the needle was well below top bar, and cooler than it was in Vegas, but I presume the altitude was the main culprit. After about 1/2 hour it was good to go again, and I just kept the rpms high so fuel would keep flowing until I got past the entrance. I had occasional trivial issues until I was out of the park and at Oakhurst (2200 feet elevation).

I have questions for dealing with this. I live in a moderate climate but take frequent trips to very hot or very high locations.

* Is the wiring for the in-tank pump present in my '79? Is it a special pump or a second just like the external one?

* When did the fuel cooler get added? I am presuming mine doesn't have it.

* Black Sheep Automotive in Vegas advised me that I should leave the key on for 30 seconds or so before trying to restart in order to push cool fuel from the tank into the lines. But when I do that I don't hear the fuel pump running; does my '79 power the pump only when the engine is running or trying to start?

* Can someone supply me photos of where/how to insulate the fuel lines?

Dennis Wilson

The wiring should be there just not attached to anything. The intank pump is different as it is attached to the strainer. As far as insulating, start with all the underhood fuel lines with the exception of the injector lines. Turning the key on for 30 seconds is redundant due to the set up in the relay which will shut the pump off after a few seconds or less. Repetitive on and off movement of the key ma help.

Dennis

SpeedBump

Did you get the job?

kary4th

The wiring for my second pump is tucked up over the fuel tank.

I was able to find an insulated "blanket" at Advance Auto. I wrapped it around the fuel hoses/lines beside and over the right cam cover as they come up to the engine. I didn't have a single problem leaving DC.



I don't know yet. I'm hoping the person they're interviewing this week isn't Jesus Christ himself. I should know soon.

Dennis Wilson

The split foam tubes that are used to insulate residential freon lines also work great if you don't mind black. JCW also sells a woven fiberglass hose that can be used to cover the lines but it will require taking the lines lose from their connections.

Dennis

BobS!

I know this thread has been done for a while but ...

I know this thread has been done for a while but ...

I have had an intermittent problem that nearly fits this general description. My engine will drop-out/cut-off for an instant after doing stop-and-go traffic then getting up to highway speeds. Or, occasionally just die in stop-and-go but start right up when I hit the key. The weird part is, this never happens when I run the AC.

Insulation is cheep I will try that. Any other thoughts?