Cleaning an electric AAR

[KTPhil]

Are you getting 12V to the AAR?

[raygreenwood]

[blues90]

Ray :
before this cold engine stall began and when I would adjust the hot idle I would have the AAR hose off at the oil bath and could feel the vacuum so it was open at this point the idle was about 300 RPM faster reading my tach I have on the dash I would keep checking to see it the AAR was closing and felt less and less vacuum . When it was closed about 8 minutes (never timed it) I would then set the idle speed on the IAD screw.

As it is now when I start cold engine always in park auto trans the RPM is 900 at that point if I place it in reverse it will stall because the idle drops below 900 to about 600 . If I start it and hold the gas pedal down to keep the idle above 900 and wait a minute then the cold idle goes up to 1300 RPM and holds while in park then when I place it in drive the idle is 900 RPM and it does not stall . I back out of the garage get back in and in park it's holding at 1300 RPM then place it reverse it's back to 900 RPM . Before this if I backed out and left it in park and let it run it took about 5 to 8 minutes for the idle to drop to the hot 900 RPM .

It never ever stalls when I'm sitting at a light in drive or anytime I shut the car down and restart in after a 1 mile drive or a 10 mile drive.
As you know once you place the trans in drive that load will drop the RPM a bit so hot in park it's 1000 RPM and in drive it's 900 RPM .

I'll go out there today and see if I have any vacuum cold on the AAR to oil bath hose . I realize with the AAR open it's extra air in the IAD past the throttle valve because at idle throttle is closed similar to the idle adjust screw you are just allowing air to bypass the throttle valve only that's a manual adjustment. I went out and didn't start the engine yet was able to draw air through the AAR hose at the oil bath and yes It has 12 volts on the AAR coil . Also I removed the hose at the AAR and did not see one bit of oil in that port it was still clean silver in color.

Here's what gets confusing , you say the extra air from the AAR is not supposed to increase the idle yet any air allowed past the closed throttle valve is just like slightly opening the throttle valve will increase the RPM . I don't mean to say it will raise the idle like a carb choke fast idle cam which is not the same thing .

[raygreenwood]

[KTPhil]

[blues90]

Ray is was comparing opening the throttle because that what I had to do to keep the cold engine from stalling. I realize opening the throttle is different yet that's what I needed to do of it stalled.

I checked the AAR this morning and could draw air through it engine off just sucking on the hose. I've been through this system several times since 2009 and never found a vacuum leak and don't recall what the idle speed was when I got the car in 85 when all the parts were still available . I changed all the hoses and gaskets because most were dried out and old . All I know is the voltage regulator was rusted and stuck so when the voltage running was low it wouldn't idle and it was smoke and pop giving it gas then it would suddenly work and all was fine well before I changed all the hoses ext.
I can't find any vacuum leaks and changed and checked everything that could leak in 2009 and went over it all again in 2012 every single wire and ECU connections and temp sensors and found nothing.

I usually only drive it twice a week short trips yet last tuesday I drove a 20 mile round trip in hot weather and just maybe that somehow freed the AAR up because now I can suck on the AAR line at the oil bath and it's open yet I have not started it since. Once it's running it runs fine and starts right up yet problem is here everything is stop and go sitting traffic with that all the idling and starting I'm running mostly off the battery when you sit there with a gen it's down to battery voltage so I need to keep it on a 2 amp charger on a 3 hour timer setting . The only time the battery gets fully charged is freeway driving which I have not done but once in 2 years. The temp sensors seem to be within range hot and cold the pressure sensor is NOS given to me with the proper Bosch number which I put on 2 years ago .

All I know at this point is it didn't stall when started cold a few months ago so my attempt was to hold the throttle open so the RPM matched what it did before this all happened then it does not stall . Had an interstate battery in it since OCT 2015 and when i took it out to check the level found it leaked got a replacement and for some odd reason no matter how much it's charged on 2 amp setting after it sets for 24 hours it's 12.62 volts the other one was 12.74 and held and I have 5mA draw so who knows what's up with that. The charging system works as if should . Since 2011 suddenly I need to key on and off 6 to 7 times to get the fuel pressure up or it won't start. Never had to do that before , I'm told it's hot soak and fuel goes back to through the pump and I have vapor only in the lines , what changed who knows . I've read many posts on adding a switch to prime the system from years ago I never needed to prime any thing just turn the key up and running. The voltmeter on the dash that still works never showed below 14.2 volts even at idle before now it does and only has 14.2 volts around 1300 RPM and above. Yet the gen runs at 2.3 times the speed of the engine RPM . Last time I went around and tightened every single FI connector pulled them out of the plug and tightened them didn't change a thing. Iv'e checked every single wire from each connector to the ECU plug all were fine and even tightened those just in case. The TS is adjusted proper the throttle does not stick it's clean also . You can't even get new head temp sensors if I needed one. Oil temp never gets above 185 F on the hottest day. Doesn't burn oil yet leaks a bit. I may have 35 K on it since I rebuilt the engine in 97 . The gas here is complete crap with their so called summer blend what ever that is and it runs worse on their summer blend. I sit here at close to 69 years old on a fixed income so I'm just happy the damn thing keeps running.

[raygreenwood]

If you are having cuel vapor kr priming issues.....that is a fuel pressure regulator issue....and possibly a pump issue.

This goes back to basic fuel mixture. Check your fuel pressure and leakdown speed after shutdown.

Again.....check basic function of the AAR. Ic its open when its cold....yes itscpossible it may be gummed up and not opening all the way.
But if its closing all the way after achandful of minites snd you are still having any issues at all.....its not AAR related. Ray

[blues90]

Ray I started it today and put it in reverse and it didn't stall . After I backed out of the garage the idle went up to 1300 RPM and soon dropped to 900 .

Last time I checked the fuel pump pressure was 6 months ago and it was 30 PSI and steady and at least 10 hours later it still had 29 PSI . I used the line from the cold start valve since I don't use the cold state at all here it never get cold enough and the port on the left last time I removed the screw the copper gasket was crap I had a spare and just don't want to rick a leak there.

It had the original fuel pressure reg until 1999 and I replaced it because I was told by a Porsche tech that worked there and was having issues passing smog maybe I should replace it didn't change a thing and it still functions no leaks and I can adjust it with no issues.

I was told the fuel pump can fail in two ways and the check valve is really not a check valve . Either the valve fails and the pump won't pump or it fails and won't hold pressure in the ring . The problem you're experiencing is due to the gas boiling after
shutdown, which forces all the gas back thru the pump, leaving the
lines filled with vapor rather than fuel. The reason it flows
backwards is that it takes 30 psi to flow forwards but only 20 psi to
flow backwards. (The valve in the pump isn't really a true check
valve; it allows reverse flow above 20 psi.)

All I know is I never had this problem before and it seems now the fix is to add a switch to prime the ring instead of turning the key 7 to 9 times. some time in 2011 this started to happen . To me it seems like it is a true check valve and should at least hold pressure at least enough to allow me to start the car after it sits for at least a few days .

I used to drive it almost everyday a 7 mile trip to work at high temps and it sat for sometimes 14 hours and always fired right up even if it sat the weekend 48 hours after a hot weather drive in a hot garage i'd turn the key once and it was running. Once it starts I can dive it 1 mile to 10 miles and let it sit for a few hours and it fires right up yet if it let it sit a day after a hot drive I need to cycle the key at least 5 times . In 1991 we drove to Vegas it was 118 F it sat for three days and fired right up.

I looked through the F--ing Bentley yet it says nothing about how long the pump should hold pressure and nothing at all about how the pump works have to read it again maybe I missed something. If the pump is crap then I will go with a 2 port like many do since a new one three port is not around and if so it costs more than I have. One would think there must be some sort of check valve that does not allow the pressure to bleed off back to the pump.

[raygreenwood]

Bluntly....whiever told you all lf that information about fuel flow, direction and fuel boiling......is absolutely full of shit.

Almost all liquids.....when under pressure.....have a higher boiling point. It is for instance why high pressure steam temp is far higher than the 212° boiling point of water.

The main valve in later pumps is a relief valve......but there is a low pressure ball check valve in the output port. Its why the pressure drops slightly after shut down. Between that and the roller cells on the pump end....and the regulator on the top end.......its common to drop to 23 psi on shut down......and not drop below about 13-15 psi within 24 houra.

30 pwi versus 20 psi downstream is pure BS.

You need to do a volume AT PRESSURE test.....and then a pressure leak down test. That.....along with watching fuel pressure stability on a REAL gauge.....will tell you everything about the pump.

With the pump wired direct to 12v and engine off....1 lpm....minimum .7tpm when running...while maintaining 28 psi....is what is required. If it cannot do that your pump is worn out.
If an accurate fuel gauge does not show a constant MAXIMUM flucuation of +/- 1 psi....which is a 2 psi spread.....if the gauge rattles more than that at idle....your fegulator or pump needs work.

There.....you have specs. The Bentley is missing so much real world/old car information as to be nearly worthless to work on D-jet.

Get these things straight and checked. What you replaced or checked a year ago.....means nothing until you check that they have not changed. Ray

[blues90]

I have a fuel/water pressure gauge that goes to 80 PSI and can be calibrated to zero . Same gauge I have always used . If I connect it to my air compressor it does not fluctuate like the other gauges do since piston type compressors are not steady . This gauge has always read dead on . I've tried other pressure gauge's on my car and see no fluctuation on this car.

The Pump is old yet even with the gauge on it driving I see no issues with pressure . From what I can tell is the check valve in the pump is just not holding pressure as it should. This is the first thing I will check just need to get the pressure up and check the gauge . If it's the check valve because I have no leaks then I can't fix that.

I understand about the volume and measuring it yet timing and how much it pumps is beyond my reach right now . I can tell you when I changed the fuel lines I had the gauge on the engine and forget to connect the return at the Y fitting I saw 28 PSI and smelled fuel had a pan under the pump area to catch the fuel when I changed the line to the tank filter to tank line and it almost filled that 2 gallon pan real quick. Not an accurate test to be sure.

I've cut the fuel line that feeds the cold start valve since I never need that and connect my fuel gauge there . The nipple with the small screw I used to use yet that washer last time was leaking and I had a spare old one just don't want to risk it again. I don't think it makes any difference where as long as it's before the regulator since I got the same reading at either one.

Odd part about that last time I checked the pressure about 6 months ago and pulled the bolt with clamp on that line which connects to the same 4 port metal line to the right side injectors it was full of fuel that it ran out so I doubt the fuel is vapor more likely the pumps check valve . Wish I had a photo of that area of the pump.

[raygreenwood]

[blues90]

I can pinch off the line before the reg I have the proper clamps to pinch off fuel lines 4 of them with the gauge I can see after key on/off to get pressure see how long it holds if check valve is in pressure/vol then I'll know . if not it's the reg I can test the relief or bypass valve by pinching off to stop the flow tells me if that works cause it may stress it and cause more harm than good since it's never been blocked .

If I had the funds I would get a 2 port like others here and a new reg nothing else leaks . if it were an injector then on cold start sitting with fuel in one or two cylinders it would miss with the extra fuel at least smoke a bit or smell the rich at the exhaust which none happen I realize it does not take much of a leak to really drop pressure yet there would be some indication if any injector was leaking enough to drop the pressure. Or smell fuel in the oil.

As long as the cold start issue does not get worse than it is now forcing me to replace something I can get a reg and pump when I can afford them then go from there

[raygreenwood]

[KTPhil]

...or just put a $20 mechanical AAR on it, after cleaning and adjusting it:

https://www.thesamba.com/vw/classifieds/detail.php?id=2002307

[raygreenwood]

[KTPhil]

Or if you want to get really tricky, maybe incorporate an rpm-sensing circuit, plus a motor driver, and a stepper motor, and achieve true idle speed control, cold or warm! Probably not worth the effort other than as an engineering challenge, but it could be made very small, perhaps hidden in an electric AAR housing!

Okay, back to reality...

[raygreenwood]

[KTPhil]

Of course, the natural extension of this has already been done in a modern digital FI system that many have fitted (Megasquirt comes to mind, though I've not done this). As the MPS/TPS supply runs its life, we may be forced into this eventually, due to the collective expense of re-engineering the original parts. Might not be an altogether bad thing, since it would give us spark, rpm, mixture control that can be mapped and tailored to many more variations. Some day, probably after I'm gone. Or maybe they will all be electric, but that's in another thread...

[raygreenwood]

[blues90]

Today I connected the fuel pressure gauge I use the line that was connected to the cold start valve. I was told last time I set the pressure to bump it to 32 PSI because of the ethanol so I set it back to 28 . First thing I did was key on/off to prime the system and the gauge was 22 PSI then I started the engine and set the pressure to 28PSI maybe add 1 PSI then shut it down . I dropped to 22 PSI then after a few minutes it rose to 24 then26 then just under 28 . I watched then 10 minutes after this happened it was back down to 26 . I've never seen this before. The engine was only run twice for maybe 5 minutes the engine was not hot easy to touch anything yet I did notice the fuel line to the gauge was warm and it was not touching the engine at all.

I can't imagine it's the gauge since it read 22 PSI priming and rose and fell when adjusting the regulator and held steady. Same gauge I used last time and it never did this. I'm going to let it sit and see how far it drops later in the day. I started at 12:30 this afternoon so maybe 5 or 6 PM I'll check.