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fuel issue with 930

I have a 78 that will start and run for a bit then shut down. I am guessing it's fuel. I inspected and found a leak at the rear fuel pump. The used the wrong clamp (screw type), so I replaced it with an efi appropriate clamp. This time the motor started and ran. The fuel line between the accumulator and the rear fuel pump started ballooning, so I shut it down. A second later it blew. Fortunately the motor was not hot.

I did some reading in the 930 manual and it states the fuel pressure should be between 2-4 bar. If it is below 2 bar it's the front fuel pump. If it's over 4 bar then it's the rear. How does this work? They are both on separate circuits.

Is there something else I should check? prior to ordering a fuel pump?

I have another fuel pump from an efi carrera. Can I use this? The 930 fuel pump is pricey!

Thanks,

John

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John- I blame and thank the longhood boys of Austin
84 911 Carrera w/ 930 t/p,efi'd,dizzy free,HFS turbo[/COLOR], 78 930 RoW no option sunroof coupe, 64 Corvette roadster, 71 911T, 73 911E, 67 Bronco survivor. 71 FJ40, 2001 Boxster
"Illegitimi non carborundum"

Last edited by sundevil64; 06-14-2011 at 01:16 PM..
Old 06-14-2011, 01:13 PM
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Whoa....

FYI.. I blew the top off of my fuel filter one time by blocking the inlet hose to the fuel distributor. Maybe you have blockage in your CIS or fuel filter?

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'87 930, 3.3 liter, K27 hybrid, Kokeln IC, Andial, B&B, Borla, 17" Supercups.
Old 06-14-2011, 07:06 PM
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Has the car been setting for a long period ? I would venture to guess a fuel filter blockage. I had ohe bad fuel relay car would run low throttle / full throttle would buck & throw you through the windshield.
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Old 06-14-2011, 08:16 PM
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The car has been sitting. I'll change the fuel filter too. I had an extra accumulator that I know to be fine that I put on. This may be a blessing in disguise. The fuel lines are in bad shape, so I an in the process if replacing them no. It's taking a little longer than I expect especially near the tunnel. I may have to remove the tranny mount to get to the connection.

Thanks foe the replies.
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John- I blame and thank the longhood boys of Austin
84 911 Carrera w/ 930 t/p,efi'd,dizzy free,HFS turbo[/COLOR], 78 930 RoW no option sunroof coupe, 64 Corvette roadster, 71 911T, 73 911E, 67 Bronco survivor. 71 FJ40, 2001 Boxster
"Illegitimi non carborundum"
Old 06-15-2011, 02:41 AM
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I've replaced the rear fuel pump, accumulator, fuel lines, and fuel filter. Still the same problem. It runs and will accelerate up, but then will shut down. It dies out as if there is no fuel going to it. Could it be the WUR or AAR?
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John- I blame and thank the longhood boys of Austin
84 911 Carrera w/ 930 t/p,efi'd,dizzy free,HFS turbo[/COLOR], 78 930 RoW no option sunroof coupe, 64 Corvette roadster, 71 911T, 73 911E, 67 Bronco survivor. 71 FJ40, 2001 Boxster
"Illegitimi non carborundum"
Old 06-15-2011, 07:45 AM
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I haven't fooled with my turbo for a while, so I am a bit rusty on troubleshooting...

What about the switch that shuts the pump off when you get too much boost.
Could it be faulty and opening at low boost?
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Old 06-15-2011, 10:23 AM
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I was just looking at that over lunch. I saw where there is a way to test it. I think I need to pull that switch and test it. I also think that I should hook up two volt meters (one to each) fuel pump and see what happens in terms of power supplied just prior to shutting down. I wonder if I can test the overboost switch in place? I would guess it grounds out and causes the overboost relay switch to kick in.

also a note, I don't have a "yellow" squarish over boost relay in the rear panel. In it's place there is a "red" round relay like one that should be in the fuel pump relay spot. I wonder if that is the problem. What is special about the "yellow" overboost relay?
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John- I blame and thank the longhood boys of Austin
84 911 Carrera w/ 930 t/p,efi'd,dizzy free,HFS turbo[/COLOR], 78 930 RoW no option sunroof coupe, 64 Corvette roadster, 71 911T, 73 911E, 67 Bronco survivor. 71 FJ40, 2001 Boxster
"Illegitimi non carborundum"
Old 06-15-2011, 10:30 AM
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I change injectors,fuel filter,2 fuel pumps, drained the tank,accumulator...etc..etc...
Same crap....Just like what u r going thru.

Answer-Fuel Head Gummed Up on me for not driving for a very long time.

Poor mans way, marvel mystery oil--if not to gummed up...

Use MMO--at every fuel up since....Not a problem since.

Last edited by wjfk32; 06-15-2011 at 10:55 AM..
Old 06-15-2011, 10:52 AM
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I just got off the phone with Brian Bodart. He let me pick his brain. I have to say he is one of the best people to talk to. I've bought some products from him for my first turbo motor and will continue to just becuase of the great service an products he provides. I wish all businesses operated like him. Brian said it may be some stuff in the fuel head because it wasn't recirculating back to the tank.

Anyway, wjfk32, did you have to remove the fuel head? How hard is that? Are all the seals reuseable or do I need to buy a kit?

Quote:
Originally Posted by wjfk32 View Post
I change injectors,fuel filter,2 fuel pumps, drained to the tank,...etc..etc...
Same crap....Just like what u r going thru.

Answer-Fuel Head Gummed Up on me for not driving for a very long time.

Poor mans way, marvel mystery oil--if not to gummed up...

Use MMO--at every fuel up since....Not a problem since.
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John- I blame and thank the longhood boys of Austin
84 911 Carrera w/ 930 t/p,efi'd,dizzy free,HFS turbo[/COLOR], 78 930 RoW no option sunroof coupe, 64 Corvette roadster, 71 911T, 73 911E, 67 Bronco survivor. 71 FJ40, 2001 Boxster
"Illegitimi non carborundum"
Old 06-15-2011, 10:59 AM
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I would guess that the boost switch is 'normally closed' which means it would show little or no resistance until it triggered and then it opens the circuit. You could just jumper across it to effectively remove it from the puzzle. If the problem goes away, you will need to determine whether the switch is bad or you really have an overboost problem.
I'm 25 miles from my turbo so I can't test what I'm saying right now.
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Old 06-15-2011, 10:59 AM
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1st thing chk if your boost switch is good...If you can test it or just switch it out..

My wrench took the freakin thing off- didn't need change seals or a kit..
Didn't want to F-with fuel head..Something I was not familar with...

Other guys can chime in..Im sure they have done it.

GL
Old 06-15-2011, 12:20 PM
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yellow relay

Quote:
Originally Posted by Shadetree930 View Post
It is the Spawn of the Devil.
LOL! Thanks for the warning.
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John- I blame and thank the longhood boys of Austin
84 911 Carrera w/ 930 t/p,efi'd,dizzy free,HFS turbo[/COLOR], 78 930 RoW no option sunroof coupe, 64 Corvette roadster, 71 911T, 73 911E, 67 Bronco survivor. 71 FJ40, 2001 Boxster
"Illegitimi non carborundum"
Old 06-15-2011, 01:40 PM
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Okay, since the "ballooning" of the fuel line would indicate a blockage somewhere as Rarelyl8 and JPNovak have mentioned to me in conversation I am going to move to the fuel distributor. I have verified the return line to the tank is clear by blowing compressed air through the return line. Hopefully I will get time in the next day or two to pull the fuel head and soak it in some solvent. I'm hoping for non-stripped screw heads and filthy solvent at the end...
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John- I blame and thank the longhood boys of Austin
84 911 Carrera w/ 930 t/p,efi'd,dizzy free,HFS turbo[/COLOR], 78 930 RoW no option sunroof coupe, 64 Corvette roadster, 71 911T, 73 911E, 67 Bronco survivor. 71 FJ40, 2001 Boxster
"Illegitimi non carborundum"
Old 06-15-2011, 04:52 PM
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Found one issue when I removed the banjo bolts on the fuel head. There were two screens in one and none in other of the others. That doesn't make sense. All the rest had one screen. I don't think this fuel head had been opened before, but you never know. Now soaking in solvent.
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84 911 Carrera w/ 930 t/p,efi'd,dizzy free,HFS turbo[/COLOR], 78 930 RoW no option sunroof coupe, 64 Corvette roadster, 71 911T, 73 911E, 67 Bronco survivor. 71 FJ40, 2001 Boxster
"Illegitimi non carborundum"
Old 06-16-2011, 06:14 AM
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Sounds like someone has removed the unit in the past and put one of the screens in the wrong hole.
If soaking is not sucessful I have a rebuilt fuel head sitting on the shelf.
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Old 06-16-2011, 01:37 PM
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Brian,
The head was fairly clean, but we will see. The screens were very clean. I just put the pin back in and it seems to move freely. Hopefully it will work. Hopefully the problem was the screen.

I am hoping this was the cause of the blockage it. I was on the fuel lead that goes to #6.
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John- I blame and thank the longhood boys of Austin
84 911 Carrera w/ 930 t/p,efi'd,dizzy free,HFS turbo[/COLOR], 78 930 RoW no option sunroof coupe, 64 Corvette roadster, 71 911T, 73 911E, 67 Bronco survivor. 71 FJ40, 2001 Boxster
"Illegitimi non carborundum"
Old 06-16-2011, 01:51 PM
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The only way to tell for sure is to remove the filter and blow through it. If there's little resistance, the filter is still okay and does not need to be replaced. But if there's more than minimal resistance, the filter is dirty and should be replaced.
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Old 06-17-2011, 10:44 AM
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Well the soaking didn't work. It's clean, but it will not stay running. darn.
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John- I blame and thank the longhood boys of Austin
84 911 Carrera w/ 930 t/p,efi'd,dizzy free,HFS turbo[/COLOR], 78 930 RoW no option sunroof coupe, 64 Corvette roadster, 71 911T, 73 911E, 67 Bronco survivor. 71 FJ40, 2001 Boxster
"Illegitimi non carborundum"
Old 06-17-2011, 02:21 PM
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Just a rookie input.

Disregarding the suspected blockage in the fuel lines. Could there be a chance that the warm control pressure is way too high hence causing the plunger to rise when the WUR is warming up, and not letting any fuel get to the injectors. If so, I guess this could be checked with the air filter off and gently pressing down on the metering plate and see if it would continue to run.
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Old 06-17-2011, 05:23 PM
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fuel issue

I'm game, but what is the "warm control pressure" and how can that be tested or regulated on a stock WUR? The air meter plate seems to be right about where it should be. It's flush, but not above the lower part of the venturi (forgive me if I' using the wrong term(s)).

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John- I blame and thank the longhood boys of Austin
84 911 Carrera w/ 930 t/p,efi'd,dizzy free,HFS turbo[/COLOR], 78 930 RoW no option sunroof coupe, 64 Corvette roadster, 71 911T, 73 911E, 67 Bronco survivor. 71 FJ40, 2001 Boxster
"Illegitimi non carborundum"
Old 06-17-2011, 06:12 PM
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