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fuel head questions

Ok so I finally got around to pulling my fuel head. From a previous thread based on the fuel pressures I was getting everyone here seemed to think it was the plunger possibly sticking and not allowing the pressure to drop. Hence it was running pig rich. So now that it's out,, the plunger seems pretty freely moving. Clearly there's some resistance there but it seems pretty smooth. How can I tell if I need it re-built ?? It is original and I"m pretty sure it's never been off the car before.. Is it worth it having it re built just on principle ?
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"Todd"
98 Tahoe ,2007 Saturn Vue
86 930 black and stock, 80 930 blue tracdog
91 Spec Miata (yeah I race a chick car)
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Old 03-25-2010, 07:02 PM
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Here's the thread that prompted this

CIS Pressure thread
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"Todd"
98 Tahoe ,2007 Saturn Vue
86 930 black and stock, 80 930 blue tracdog
91 Spec Miata (yeah I race a chick car)
"life"ll kill ya" Warren Zevon
Old 03-25-2010, 07:32 PM
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Is it running rich on boost? Your intercooler seal or something else might be leaking off air flow.

You might check with Larry at CISFLOWTECH he is the guy that rebuilds and can modify you FD for more fuel.

If you do not have any air leaks and all your pressures check out including your hot control pressure, then the FD might be suspect.

Anyway, a fresh head with clean and balanced (new?) injectors is a good investment in the name of keeping your motor from going lean in one cylinder.

If all is sound and you are rich everywhere, you might try resetting your CO at the metering arm.

Do you have any mods that might be changing you motors air flow parameters?
Old 03-25-2010, 08:16 PM
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Kieth,
No mods, it's the same with the stock WUR and the digital one,.. runs rich all the time as well as NO boost. Main issue was when blipped the fuel pressure wouldn't drop no boost just idle to say 3000 rpm. The collective mind trust here said it's pointing towards the fuel head.
I think I'll get it rebuilt just to be on the safe side, it is 34 years old!!
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98 Tahoe ,2007 Saturn Vue
86 930 black and stock, 80 930 blue tracdog
91 Spec Miata (yeah I race a chick car)
"life"ll kill ya" Warren Zevon
Old 03-25-2010, 08:45 PM
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What do you mean by fuel pressure?

When you say fuel pressure do you mean 'system pressure'?

If so SP should not go up or down and should stay fixed. If it is elevated there cold be something in the heads regulator that might be binding or there could be something in the fuel return line to the gas tank somewhere that might be causing a restriction?

Larry also rebuilds WUR's and is the only guy that seems to be able to get info and factory parts from Bosch.
Old 03-25-2010, 09:45 PM
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I would suspect the WUR first, sounds like your control pressure is staying too low. Have you checked the control pressure? I have a bench tester for the FD if you would like it checked.
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Last edited by lite75; 03-25-2010 at 09:54 PM..
Old 03-25-2010, 09:49 PM
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Quote:
Originally Posted by 911st View Post
Is it running rich on boost? Your intercooler seal or something else might be leaking off air flow.

You might check with Larry at CISFLOWTECH he is the guy that rebuilds and can modify you FD for more fuel.
What does Larry typically charge for a rebuild?
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Old 03-26-2010, 04:55 AM
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Larry is a great guy so you might email or call him to be sure but I think just over $500 for the FD and about $200 for the WUR.
Old 03-26-2010, 08:18 AM
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Quote:
Originally Posted by 9dreizig View Post
Kieth,
No mods, it's the same with the stock WUR and the digital one,.. runs rich all the time as well as NO boost. Main issue was when blipped the fuel pressure wouldn't drop no boost just idle to say 3000 rpm. The collective mind trust here said it's pointing towards the fuel head.
I think I'll get it rebuilt just to be on the safe side, it is 34 years old!!
Todd this is a little hard for me to understand what you are trying to say.

I think you are saying:

Stock and D-WUR (new out of the box) both show the same rich condition at all points pre-boost and 'on'-boost.

Control Pressure (not fuel pressure) dose not drop with throttle blipping off idle.

Control Pressure dose drop after 3000rpm.


If this is true, it sounds like both the stock WUR and D-WUR have been tried. Both are probably set to operate as stock. Both show the same rich setting. Thus, it may not be the WUR as both are showing the same response.

The stock 930 WUR dose not lower CP when the throttle is biped. It only dose so when about 5psi of boost is reached. I am not sure how the D-WUR is programed in this regard but I suspect that out of the box it is set to work as the stock WUR. If your CP dose drop at 3000rpm that is consistent with normal boost enrichment which is typically trigered at about 5 psi of boost. Thus, all sounds ok in that regard.

If the stock and D-WUR have the same response it dose not sound like a WUR issue.

If system pressure (fuel pressure?) checks out I would not suspect the FD per say.

If your hot control pressure checks out I would not suspect the WUR per say.

At almost sounds like you could just reset the idle CO to spec and everything should fall back into place.

Intake air temperature changes can effect CO. If your CO was set on a very cold day, CO will be rich on a very warm day. If CO was set to adjust around another issue like an intake leak, restrictive fuel filter, and or dirty FD and this is later corrected. The CO might change.

I would try adjusting the CO (idle air fuel ratio) using the factory adjustment at the metering arm and see if this puts you back where things belong.
Old 03-26-2010, 08:44 AM
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Todd,
Your 930 is a '80 Euro correct? The fuel head you have pictured is not a Euro fuel head. Not that this matters, just an observation.
I have a good Euro fuel head that I use on my WUR test stand that I can loan you. If my fuel head fixes your problem and you want to keep it we can work it out.
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Old 03-26-2010, 09:11 AM
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Brian,
My 80 (79 engine) is Euro.. However this is the 86 that we are talking about.
Keith.. The other thread explains pretty well (at least I think) the pressures. Another note I have adjusted to the CO screw to the point where it's too lean to idle and won't start.. it still runs rich at speed.

I am going to have the unit flow checked (should only be around $50) and rebuilt if needed, that seems to be the prudent thing to do..
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98 Tahoe ,2007 Saturn Vue
86 930 black and stock, 80 930 blue tracdog
91 Spec Miata (yeah I race a chick car)
"life"ll kill ya" Warren Zevon
Old 03-26-2010, 09:33 AM
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