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korpela
Samba Member
Joined: December 31, 2015
Posts: 5
Location: Seattle
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 Posted: Fri Feb 19, 2016 8:46 am Post subject: bus stalling out |
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I have a 1977 bus and it will start and run a little bit then stall
out, thinking it may be the fuel pump, just started doing this, any ideas?
peace,
Brian |
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Randy in Maine
Samba Member
Joined: August 03, 2003
Posts: 34890
Location: The Beach
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Tcash
Samba Member
Joined: July 20, 2011
Posts: 12843
Location: San Jose, California, USA
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| Posted: Fri Feb 19, 2016 9:41 am Post subject: Type IV (4) testing FI fuel pump circuit running |
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Take a look at Amskeptics:
Double Relay Explained. . . In Color!
| Amskeptic wrote: |
When the engine starts, we release the ignition key. The starter circuit drops out. The CSV and TTS are cut off as well. And inside the double relay, the fuel pump relay is going to want to drop out as well. . . . but, it doesn't. Thanks to the Air Flow Meter, which has determined that the engine is running all by itself, the power relay voltage that has been supplied to terminal #88a to the AFM all of this time, now gets to return to the fuel pump relay through 86b, illustrated with a shocking blue/red striped wire. There is a diode inside the relay that prevents the AFM voltage from running out to try to engage the starter and cold start valve, so all that happens is that the fuel pump and AAR are allowed to continue to run only so long as the AFM is reading air flow. If you stall the engine, well, consult "Ignition On - Engine Off" diagram.
Engine Running:
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The fuel pump is powered by the starter while cranking.
Then when the flap in the air flow meter AFM opens slightly the fuel pump points close and the fuel pump is powered by the AFM.
Key in the run position pull the air filter out and with a chopstick open the flap inside the AFR and listen for the fuel pump to come on.
Pump does not come on:
Pull the wire off the coil that goes to the distributor while testing. So you do not fry the points or coil.
Key on AFM flap propped open, check for
12v on terminal 88z
12v on terminal 86c
12v on terminal 88a
12v on terminal 86b
Grnd on 85
If all above is ok
Back pin terminal 36 & 39 on the AFM you should see 12v on both terminals
12v on 39 but not on 36
Pull the cover off the AFM and clean the points. If needed slightly bend the points arm so the points make contact. |
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korpela
Samba Member
Joined: December 31, 2015
Posts: 5
Location: Seattle
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| Posted: Fri Feb 19, 2016 10:16 am Post subject: Re: bus stalling out |
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I can't say that I do, but I'll give it a go, I really need to learn how
to do some of this stuff, Thanks for your input, Randy  |
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korpela
Samba Member
Joined: December 31, 2015
Posts: 5
Location: Seattle
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| Posted: Fri Feb 19, 2016 10:26 am Post subject: Re: bus stalling out |
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| Hey Tcash, nice charts, thanks a whole bunch, I'm going in |
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