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79 Bus fuel injection / Fuel pump Question
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cmracs
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PostPosted: Sat May 22, 2010 2:35 pm    Post subject: 79 Bus fuel injection / Fuel pump Question Reply with quote

Hi. Could someone please give me some advice? I have been working on my son's 79 California Bus for a few months now... Rebuilt the engine completely, all new fuel and vacuum lines, new fuel injectors, the works. It still has the same problems as when it died a few months ago. It will only start and run for a few brief moments and at an extremely accelerated idle - actually it won’t idle at all. I have to rev it to about 2000 rpm to get it to run. During the process of testing all of the fuel injection related parts (electrical and mechanical) according to my Bently manual, I forgot to put the 7 pin connector back on the air flow meter. I started the car without that plug connected and it idles better than when it is connected! With a fuel pressure gauge connected, I start the bus without the 7 pin connector plugged in and the gauge reads 0 PSI. I plug in the 7 pin connector to the air flow meter and the fuel pressure reads about 35 PSI and the engine revs to a couple thousand RPM and then dies. I am completely baffled. By the way, I’m glad the Bus died on my son when it did. All of the fuel lines were cracked and leaking… lots of oil leaks too… I would really appreciate any advice anyone could offer.

Thanks , Bill Tucker
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cmracs
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PostPosted: Sat May 22, 2010 4:17 pm    Post subject: Engine running with Zero fuel pressure Reply with quote

Hi again. I was hoping someone would have some insight on this strange phenomenon: A fuel injected engine running without fuel pump pressure… Anyone else ever try (accidentally) running their engine with the air flow meter unplugged?
Thanks again.
Bill
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dubluvv
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PostPosted: Sat May 22, 2010 4:18 pm    Post subject: Reply with quote

Did you go through the process of testing the AFM? Sounds like your AFM is screwed up. How the system works is, while cranking the engine, the fuel pump gets power from the starter. After the engine starts, the fuel pump gets its power from the AFM.

Someone else with similar symptoms:
http://www.thesamba.com/vw/forum/viewtopic.php?t=358286&highlight=afm

Also, may want to look here:
http://www.thesamba.com/vw/forum/viewtopic.php?t=369815
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maximan1
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PostPosted: Sat May 22, 2010 4:21 pm    Post subject: Reply with quote

Hi.

You have a vacuum leak. Exactly the same symptoms I had with my bus, turns out the intake manifold boots were kinda non existant. I replaced them, bus runs great. Whats happening is that your bus is getting air past the air flow meter.

When you unplug the AFM the bus automatically goes into super duper rich running mode, and it idles fine. Check and recheck all vacuum lines, because one of them is bad.
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cmracs
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PostPosted: Sat May 22, 2010 4:24 pm    Post subject: Reply with quote

Thanks for the advice. I did test the AFM. I tested the double relay. I have checked every connection for continuity from the ECU plug back through every component in the system. The Bently manual has been a big help with all of these tests. I understand how the system works. That is why I am completely baffled by the car idling with Zero fuel pump pressure... Thanks again, Bill
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cmracs
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PostPosted: Sat May 22, 2010 4:29 pm    Post subject: Thanks Maximan Reply with quote

I didn't realize the Bus would run without fuel pump pressure. What you are saying makes sense though and I haven't really checked for a vacuum leak because I installed all new vacuum lines and new intake boots as well. I will find it!! (I'll report back when I do.) Thanks again.
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dubluvv
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PostPosted: Sat May 22, 2010 4:29 pm    Post subject: Reply with quote

maximan1 wrote:
Hi.

You have a vacuum leak.


Could very well be, but that does not explain zero fuel pressure.
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'76 Westy 2.0L FI "Lucy" Project Thread
'84 Rabbit L Diesel - Potential Greasecar Project

chazz79 wrote:
"Aw honey, I got another one of those bay-bus things on my shoe again...dammit"
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pkrboo
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PostPosted: Sat May 22, 2010 4:31 pm    Post subject: Reply with quote

The vac leak could be at the fuel pump regulator thus giving zero FP.
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dubluvv
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PostPosted: Sat May 22, 2010 4:39 pm    Post subject: Reply with quote

pkrboo wrote:
The vac leak could be at the fuel pump regulator thus giving zero FP.


Well, I don't know. While doing a fuel pressure test, if you remove the vacuum line to the fuel pressure regulator (hence making a huge vacuum leak?), the fuel pressure goes up. Am I interpreting this right? That's what happens when I pull my vacuum line off the FPR, the pressure goes up near 36 PSI.

http://www.itinerant-air-cooled.com/viewtopic.php?t=213
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'76 Westy 2.0L FI "Lucy" Project Thread
'84 Rabbit L Diesel - Potential Greasecar Project

chazz79 wrote:
"Aw honey, I got another one of those bay-bus things on my shoe again...dammit"


Last edited by dubluvv on Sat May 22, 2010 5:05 pm; edited 1 time in total
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cmracs
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PostPosted: Sat May 22, 2010 5:01 pm    Post subject: Reply with quote

Hi Dubluvv. I pulled the vacuum line from the pressure regulator and plugged it. I get between 40-45 PSI on the fuel pressure gauge when I disconnect the vacuum line to it. According to the Bently manual I believe this pressure is a little high. My fuel pressure gauge might not be perfectly calibrated though. The vacuum line on the pressure regulator activates a diaphram that allows fuel back into the tank at about 30 PSI. without this vacuum assist on the regulator, the fuel pressure is higher. So far I have disconnected and plugged every vacuum line, emissions line, etc.. I still can't get this beast to run right....
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Randy in Maine
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PostPosted: Sat May 22, 2010 5:56 pm    Post subject: Reply with quote

You need a better guage.....


Have you been through the double relay?

http://www.itinerant-air-cooled.com/viewtopic.php?t=5460
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Wildthings
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PostPosted: Sat May 22, 2010 8:16 pm    Post subject: Reply with quote

A bus will never have zero fuel pressure unless the tank is empty. The fuel tank sits high enough to supply enough fuel for it to idle without the pump running. The high tank also makes for fantastic fires once a fuel line lets go.

A high idle speed mean extra air has to be getting into the engine from somewhere. I am not sure how these two symptoms fit together, something just doesn't seem right.

I think you need to look for a major vacuum leak, like a large diameter hose that blew off in a back fire.
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RocketRod
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PostPosted: Sat May 22, 2010 8:40 pm    Post subject: Reply with quote

Check your brake booster line on the other side of the engine bay back to the booster. That line and the larger lines will cause what you are describing too. You may not hear the leak until you get under the bus. The Bentley has a specific test for the FPR and for fuel quantity through it. hopefully you have done those. One thing I will tell you is to not assume anything is working correctly on the Fi system until you have checked every item. Save yourself squat loads of frustration and do them in sequence as outlined.
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patayres
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PostPosted: Sat May 22, 2010 9:01 pm    Post subject: Reply with quote

I would go to work with a spray bottle of soapy water and look for vacuum leak if the brake booster line checks out and all lines are attached. Throttle body gasket, s boot, intake manifolds, etc. Is there an EGR setup on the engine?
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BUSBOSS
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PostPosted: Sat May 22, 2010 11:08 pm    Post subject: Reply with quote

patayres wrote:
s boot


I like this possibility. Had similar problems in the past and this was it. Check all of those accordion folds - there might be a leak hiding in there.
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cmracs
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PostPosted: Sun May 23, 2010 9:21 am    Post subject: Thank You Reply with quote

Thank you all for your replies. I haven't yet located the vacuum leak but I'm back at it this morning. I'll check the S boot and every thing else with soapy water. I did use all new gaskets, hoses, boots, etc.. when I put the engine back together. This idle problem is what prompted me to rebuild the engine 4 months ago. This and the fuel and oil bleeding out of the engine compartment... Thanks for the links posted above - Lots of good info there.
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cmracs
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PostPosted: Sun May 23, 2010 1:51 pm    Post subject: Reply with quote

Not S boot, not brake assist. I did find a leak at the cold start valve. The valve body was loose in the mounting bracket and when I sprayed carb cleaner on the valve the idle went to about 4000. I coated the area around the cold start valve with 60 sec. epoxy and it runs a little better now but not much. Yesterday i emailed Tram before I posted anything here.. I got the following email from him :

Bill- Are you 100% certain that this isn't an ignition issue? Check spark and check power to the coil. Also, if this is a California bus, it likely has electronic ignition with the Hall sender and Telefunken or Bosch ign. module box, both of which can cause a similar issue.
Best, George aka Tram

I checked for spark and power to the coil. The advance mechanism in the distributor is kinda squirly.. I'll look further into it.

Thanks Again all.
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PostPosted: Thu May 16, 2013 8:47 am    Post subject: Alright I bought a bus. Now just getting her Idling.... Reply with quote

I picked up a 1976 Westy a bit ago. It came without a key so i had to purchase a new ignition.. I had to buy a new battery and fuel pump and we had the bus up and running! We would start it up and drive it to the end of the drive driveway about 100 times. then she would die.

Now i am just basically trying to get her to idle. I brought it to a shop to have vacuum and fuel lines redone. we got the bus to idle for about 9 seconds or so and it starves it self out

So we did a fuel pressure test. We also put a fuel filter after the fuel pump so we could see volume and really make sure it was pumping great.
turned the key and pressure was good. so good that it blew apart the fuel filter.

what we came to the conclusion of was when we start the bus the fuel pump is getting 12 volts and pumping great. now after that its stops running. hence why it runs for a little bit and then dies. we checked the double relay and it seems like its getting power with a light tester. is there something that tells the fuel pump to stay on? also when i first got the bus it didn't come with a key. could i have installed the ignition wrong so the fuel pump doesn't stay on?
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Wildthings
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PostPosted: Thu May 16, 2013 9:16 am    Post subject: Reply with quote

The fuel pump side of the double relay gets a signal from the starter solenoid to power the fuel pump while you are cranking the engine. As soon as you get air flow and the door in the AFM begins to open, a set of points in the AFM closes and that should signal the double relay to stay in the "on" position and thus keep the fuel pump running.

If you remove the air cleaner and stick a pencil into the AFM and open the door the fuel pump should run if the ignition is turned on.
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