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JSMskater
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Joined: February 01, 2006
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Location: Murrieta California
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 Posted: Sat Aug 29, 2009 1:58 pm Post subject: 1978 FI Beetle |
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howdy all --
I'm helping out a friend and neighbor with his 78 FI vert. I'm pretty proficient in D-jet but this is L-jet so I was making sure that I'm giving him the right advice and all that.
I'm sure he'll pop in here and add additional information but basically the story is it was running great and then one day started running like crapola. bogging down, couldn't get it up hills, and hard starting.
I came out to take a look and discovered several things. First off, it was douching fuel at both rails. When I first heard him explain his symptoms to me I was already thinking either the fuel filter was clogged or the AAR was bunk or his voltage/ignition system was going nuts.
After some VOM testing, the Air flow meter was reading slightly high-- 100 ohms higher than spec -- on the 6/9 pins. The AAR was closed dead cold, so that was bad too. However it's when I checked the fuel pressure that things started making a bit more sense:
I put my pressure gauge on and had him turn the key (spark disabled of course) and my gauge pegged on the needle, past 60 PSI! 
According to the Muir book pressure should be at 35psi on L-jet correct? This leads me to suspect the fuel pressure regulator is shot and needs replacement. The leaking fuel lines are due to the excessive pressure, and the bogging down is a sign of pig rich mixture. It smelled rich when he tried to start it for me. It did start and run but ran like piss.
Am I correct? Does this all sound logical? Are there any other components I should check? I've advised him to get a new AAR, replace all the fuel lines, replace the fuel filter, and replace the pressure regulator. I'm also going to replace some of the L-jet plugs since they're falling apart. Good?
thanks guys!
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Tram
Samba Socialist
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| Posted: Sat Aug 29, 2009 2:31 pm Post subject: |
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Joe, that excess pressure sounds like there's a bad kink in the fuel system hoses somewhere, most likely on the return side.
That AAR can probably be removed, soaked in Diesel fuel after freeing it up with carb cleaner and made to work again.
There's an outside chance that someone could have adjusted it all the way closed. There's a 6 or 7mm nut on the back of the biscuit that you can loosen, then move the little stud it locks down use to adjust the AAR opening cold. There may be a latent vacuum leak somewhere else that caused some genius to close off the AAR.
On the L-Jet system, ALL intake air except for the small amount added by the cold AAR, MUST enter through the air flow meter.
The fuel pressure regulator is vacuum operated/ adjusted on these unlike an L-jet car.
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zoti
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Joined: December 26, 2007
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Location: Plano, TX USA
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| Posted: Sat Aug 29, 2009 2:45 pm Post subject: |
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| From under the car disconnect the return line from the pressure regulator and try to blow through it. This will tell you if the fuel line is blocked on the return side. |
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JSMskater
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| Posted: Sat Aug 29, 2009 2:53 pm Post subject: |
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| Tram wrote: |
Joe, that excess pressure sounds like there's a bad kink in the fuel system hoses somewhere, most likely on the return side.
That AAR can probably be removed, soaked in Diesel fuel after freeing it up with carb cleaner and made to work again.
There's an outside chance that someone could have adjusted it all the way closed. There's a 6 or 7mm nut on the back of the biscuit that you can loosen, then move the little stud it locks down use to adjust the AAR opening cold. There may be a latent vacuum leak somewhere else that caused some genius to close off the AAR.
On the L-Jet system, ALL intake air except for the small amount added by the cold AAR, MUST enter through the air flow meter.
The fuel pressure regulator is vacuum operated/ adjusted on these unlike an L-jet car. |
It just occurred to me I should add something else -- I checked the pressure at the fuel line coming out of the firewall on the delivery side -- before the regulator  this implies that perhaps there's a kink or blockage on that side no? is it possible the pump has gone haywire? We're going to replace the fuel filter as well. does where I tested for pressure change anything/ assessments?
I will check out the AAR and see if it can be resurrected
thanks!!
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Randy in Maine
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| Posted: Sat Aug 29, 2009 3:06 pm Post subject: |
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Doesn't really matere where your test the fuel pressure. It is a "loop".
I also like a kinked fuel return line. |
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JSMskater
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| Posted: Sat Aug 29, 2009 3:17 pm Post subject: |
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| Randy in Maine wrote: |
Doesn't really matere where your test the fuel pressure. It is a "loop".
I also like a kinked fuel return line. |
but the loop isn't closed. That's my point. I did it with the second half of the loop disconnected. I put the gauge right into the fuel line that comes out of the firewall that normally attaches to the fuel rail on the drivers side. Should I hook it all back up and find a "passive" point to measure pressure?
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Randy in Maine
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JSMskater
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Location: Murrieta California
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| Posted: Sat Aug 29, 2009 4:02 pm Post subject: |
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thanks for the links -- I'll read through them
It cant be a loop if I disconnect it! this is my point. the way I hooked up the gauge is a direct shot. tank, pump, fuel line, gauge. it doesn't go past the gauge or continue. I disconnected the rest of the fuel circuit from the supply line, using the supply line as my point of access with the gauge.
In any case it doesnt matter since it appears that the method for testing pressure on D-jet isn't going to work here, since the regulator needs proper vacuum to work. I'm going to have to re-do it and check back.
You think you hook up the gauge near the cold start valve? I'll remove the fuel line going to the cold start valve and plumb the gauge there and re-hook up the fuel circuit. if it's still at 60psi I'll check for kinks, and if not then we'll move on from there.
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Tram
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| Posted: Sat Aug 29, 2009 4:10 pm Post subject: |
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| JSMskater wrote: |
thanks for the links -- I'll read through them
It cant be a loop if I disconnect it! this is my point. the way I hooked up the gauge is a direct shot. tank, pump, fuel line, gauge. it doesn't go past the gauge or continue. I disconnected the rest of the fuel circuit from the supply line, using the supply line as my point of access with the gauge.
In any case it doesnt matter since it appears that the method for testing pressure on D-jet isn't going to work here, since the regulator needs proper vacuum to work. I'm going to have to re-do it and check back.
You think you hook up the gauge near the cold start valve? I'll remove the fuel line going to the cold start valve and plumb the gauge there and re-hook up the fuel circuit. if it's still at 60psi I'll check for kinks, and if not then we'll move on from there. |
Yes, the cold start fuel line is fine. Sounds like the pump works GREAT! 
Let us know what the fuel pressure really is, and we'll go from there.
You can pull the vacuum line off the pressure regulator and sniff for gasoline. If there's gas on the vacuum side of the regulator, ist kaputt.
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| Bryan67 wrote: |
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zoti
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| Posted: Sat Aug 29, 2009 4:44 pm Post subject: |
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Of course you get 60 PSI if you connect the gauge in line with the fuel pump. That's why you have a pressure regulator. To regulate the pressure.
Test it when it is connected instead of the cold start valve. |
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JSMskater
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Location: Murrieta California
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| Posted: Sat Aug 29, 2009 5:11 pm Post subject: |
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| zoti wrote: |
Of course you get 60 PSI if you connect the gauge in line with the fuel pump. That's why you have a pressure regulator. To regulate the pressure.
Test it when it is connected instead of the cold start valve. |
yeah i realized after I got back home that it was a bad way of testing it. I'm used to having a handy nipple on the fuel rail for me to hook my gauge to but couldn't find a suitable place -- so in my ignorance I just put it on the delivery side of the loop. *doh* moment when I got home and thought about it.
Geo I'll sniff that line and redo everything.
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JSMskater
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| Posted: Sun Aug 30, 2009 3:17 pm Post subject: |
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Ok--
so today I replaced all the fuel lines in the engine bay, they were all pissing fuel. Hooked up the pressure gauge to the hardline where the cold start injector normally goes, and got some odd readings:
on the first crank of the engine, it pegged at about 40, and then came down to 35, where it held for about 10 seconds, (and still cranking) it steadily bled down to about 5psi. We cranked it several times and it never came back, the pressure just wouldn't build up.
I pulled the vac line off the pressure regulator and sniffed it, and didnt smell any fuel. I am hearing a vacuum leak somewhere though, I can hear it make a hissing/cyclical thump as we cranked it. What I don't know is where the hell it is. He's going to buy a whole bunch of hose and I'm gonna replace all the vacuum lines.
I'm suspecting either the vacuum pull is too weak during cranking, the vac lines are just shot and therefore not allowing strong vacuum, or the regulator itself is shot.
other tests I did include hooking up an LED to the injector plugs, they all pulsed well and so I know the injectors can get fuel (I had them disconnected -- I didnt want to try to start the engine)
I've got the AAR here and I'm going to clean it up and play with it:
Geo- I'm thinking I'll hook up a battery to the electrical connector on the AAR and see if it opens and closes at all (after cleaning) and if it doesn't then do the adjustment and have it closed.... when? that's my question. I don't really know how long the electrical element inside takes to close it, or if I should base my timing off the average warm up time for the engine...? is there a spec out there?
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Tram
Samba Socialist
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Posts: 22728
Location: Still Feelin' the Bern- Once you've felt it you can't un- feel it.
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| Posted: Sun Aug 30, 2009 3:27 pm Post subject: |
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| JSMskater wrote: |
Ok--
so today I replaced all the fuel lines in the engine bay, they were all pissing fuel. Hooked up the pressure gauge to the hardline where the cold start injector normally goes, and got some odd readings:
on the first crank of the engine, it pegged at about 40, and then came down to 35, where it held for about 10 seconds, (and still cranking) it steadily bled down to about 5psi. We cranked it several times and it never came back, the pressure just wouldn't build up.
I pulled the vac line off the pressure regulator and sniffed it, and didnt smell any fuel. I am hearing a vacuum leak somewhere though, I can hear it make a hissing/cyclical thump as we cranked it. What I don't know is where the hell it is. He's going to buy a whole bunch of hose and I'm gonna replace all the vacuum lines.
I'm suspecting either the vacuum pull is too weak during cranking, the vac lines are just shot and therefore not allowing strong vacuum, or the regulator itself is shot.
other tests I did include hooking up an LED to the injector plugs, they all pulsed well and so I know the injectors can get fuel (I had them disconnected -- I didnt want to try to start the engine)
I've got the AAR here and I'm going to clean it up and play with it:
Geo- I'm thinking I'll hook up a battery to the electrical connector on the AAR and see if it opens and closes at all (after cleaning) and if it doesn't then do the adjustment and have it closed.... when? that's my question. I don't really know how long the electrical element inside takes to close it, or if I should base my timing off the average warm up time for the engine...? is there a spec out there? |
Sounds like the fuel pump is on its last legs- a burst of power then slowly bleeding off. Check and see what happens to fuel delivery into a container- See if it starts off strong, then just fades away while cranking.
Could also be the relay cutting juice.
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| Bryan67 wrote: |
| Just my hands. And a little lube. No tools. |
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JSMskater
Samba Grease Gorilla
Joined: February 01, 2006
Posts: 5362
Location: Murrieta California
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| Posted: Sun Aug 30, 2009 3:37 pm Post subject: |
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| Tram wrote: |
| JSMskater wrote: |
Ok--
so today I replaced all the fuel lines in the engine bay, they were all pissing fuel. Hooked up the pressure gauge to the hardline where the cold start injector normally goes, and got some odd readings:
on the first crank of the engine, it pegged at about 40, and then came down to 35, where it held for about 10 seconds, (and still cranking) it steadily bled down to about 5psi. We cranked it several times and it never came back, the pressure just wouldn't build up.
I pulled the vac line off the pressure regulator and sniffed it, and didnt smell any fuel. I am hearing a vacuum leak somewhere though, I can hear it make a hissing/cyclical thump as we cranked it. What I don't know is where the hell it is. He's going to buy a whole bunch of hose and I'm gonna replace all the vacuum lines.
I'm suspecting either the vacuum pull is too weak during cranking, the vac lines are just shot and therefore not allowing strong vacuum, or the regulator itself is shot.
other tests I did include hooking up an LED to the injector plugs, they all pulsed well and so I know the injectors can get fuel (I had them disconnected -- I didnt want to try to start the engine)
I've got the AAR here and I'm going to clean it up and play with it:
Geo- I'm thinking I'll hook up a battery to the electrical connector on the AAR and see if it opens and closes at all (after cleaning) and if it doesn't then do the adjustment and have it closed.... when? that's my question. I don't really know how long the electrical element inside takes to close it, or if I should base my timing off the average warm up time for the engine...? is there a spec out there? |
Sounds like the fuel pump is on its last legs- a burst of power then slowly bleeding off. Check and see what happens to fuel delivery into a container- See if it starts off strong, then just fades away while cranking.
Could also be the relay cutting juice. |
Ok I'll do that test to the pump -- maybe this is a dumb question, but why then when I hooked up the gauge directly to the delivery side did I get 60PSI and then it stayed there? I don't doubt you, I just want to know the theory behind it.
also, why would the relay cut juice? again, just wanting to learn it. Would this indicate a faulty relay or is it supposed to work like that?
finally, and update on the AAR situation. Dunked it in diesel and let it sit, and used some WD-40 and carb spray. cleaned it up and it was still closed. I took the nut off and wiggled it, and I could see a small little notch, which I then stuck a flat head screwdriver into. I was able to gently pry the little (apparently) spring loaded disk inside to full open, but it will not stay there. I take the screwdriver out and it slams shut.
is it dead or am I doin it wrong?
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Tram
Samba Socialist
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Location: Still Feelin' the Bern- Once you've felt it you can't un- feel it.
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| Posted: Sun Aug 30, 2009 3:56 pm Post subject: |
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Tighten the nut back down while holding the passage open. Then heat it up with a heat gun or hairdryer and see if it starts closing.
Check for continuity.
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| Bryan67 wrote: |
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JSMskater
Samba Grease Gorilla
Joined: February 01, 2006
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Location: Murrieta California
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| Posted: Sun Aug 30, 2009 4:41 pm Post subject: |
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| Tram wrote: |
Tighten the nut back down while holding the passage open. Then heat it up with a heat gun or hairdryer and see if it starts closing.
Check for continuity. |
sounds good. if it matters at all I measured the resistance across the pins and got 380 ohms
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Randy in Maine
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| Posted: Sun Aug 30, 2009 5:54 pm Post subject: |
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See if the fuel pump will pump out about 1L of fuel in 30 seconds.
Do the test to see if the FP or the FPR is the bad one. |
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JSMskater
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| Posted: Sun Aug 30, 2009 9:01 pm Post subject: |
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will do
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JSMskater
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| Posted: Tue Sep 08, 2009 3:42 pm Post subject: |
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ok so an update:
went to check the pump, and found out the damn thing isn't even coming on. I *think* this is because I have several things disconnected in the engine compartment, and looking at the wiring diagram is appears that the pump shares a circuit with the thermo time switch and cold start valve as well as a dedicated pump switch.
edit* looking at the FI manual linked above, I can force the pump to come on without turning the engine over. I'm gonna try that.
the AAR is shot. I tried holding it open and then tightening the adjusting nut but it wont stay open. it just snaps shut again. Geo, you have a PM
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Randy in Maine
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