Never before seen mess

chillman88

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A number of months ago, I put a mechanical fuel pressure gauge on my '93, mounted to the cowl so I could see it when driving.
. At the time, it had my RD2-110 IP on it. So, oversized pump etc.
Put the fuel gauge on the output side of the fuel filter. This setup had a stock mechanical lift pump, stock filter etc.

At idle, it was perhaps 4.5 PSI. WOT 3.5. Never dropped below 3.5 PSI no matter what I did.

That right there is why I like the mechanical pumps. If I need to add a 'primer' pump, so be it. But I'm not getting rid of the mechanical pump.

All I will say is running my E-pump the filter light came on about 70-75 in the hills of PA or any time I was really pushing it while towing. Haven't had any issues with the mechanical one.
 

chillman88

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Hmm... that's a 52 gph pump, too. :dunno

I haven't checked the fuel pressure on my Facet 40285 yet, but the filter light does not come on (and the light does work). That's only rated at 33 gph.

Quite honestly I didn't verify I had a large enough gauge running to it. I had whatever the PO was running the mr. gasket pump with. Ran fine until I asked it to work. Sounds lazy but running new wires and a relay for something that might not be any better isn't worth it to me when my mech. pump runs fine. Ask the guys at the rally last year. It ran great around town empty, it just wasn't happy about the hills coming home.
 

DrCharles

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That is quite possibly the problem - but needs verification with a decent meter before making the diagnosis.

The output of electric fuel pumps drops VERY sharply as the supply voltage (at the pump terminals) goes from 13.8 volts to 12.0 or lower. I learned this by experiment when I was modifying a factory turbo fuel-injected car for more boost (and therefore not only more fuel required, but at a higher pressure). The factory wiring was just adequate for the original pump and demand. Not the bigger Walbro pump working harder.
 

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