DNMakinson

iTrader: (3)

Well, I've gone through this (4) times now.

MS3X in a '99 with return style fueling conversion.

Set car up with 0.3 Seconds delay before priming pulse.
Use a heavy priming pulse.
Take key directly from OFF to START
Car starts within 1 second of cranking time.

Then, fuel pump seems to get old, and I can hear what seems to be air exhausting into tank (via return line) during a 2 second KEY ON. At that point, the car does not get the priming pulse and starting characteristics change considerably in a negative direction. This tends to happen in the fall????? Tank venting is in place.

Put in new fuel pump. First OEM to DW100. Then DW100 to DW200. Then DW200 to Walbro 190HP. First 2 pumps really were bad, as indicated by lack of fuel up top (high load / high RPM). No indication that the present pump is bad in that regard, neither the DW200 IIRC). This is 3 new pumps in 5 years.

So, now I am resolved to OFF to ON until CEL goes off. Priming Delay set to 1.5 seconds. Now I am back to consistent and quick starts. I realize that most people do this, and I can live with it, but I don't understand why it seems not necessary with a brand new pump, but does not take long to be needed. As I have stated elsewhere, OEM like starts should be possible, and that means OFF to START in one motion.

No indication of a hole in the FPR diaphragm. Used unit from UK NB return style set-up.

Should we expect aftermarket pumps to take time to spin up?
Could my issue be somewhere else?
Think the fuel temperature could be an influence?
I don't notice any indications of a bad relay (as in stalls or dies during normal driving. I'm I in denial here?

DNM

technicalninja

You are describing loss of pressure after shut off.This is what I call "static" pressure.
FI fuel pumps have a check valve in them that should hold static pressure for days.
They normally last a long time, 10 years is not uncommon.
Having multiple failures with different brands is double headed weird.
Overnight FP test would be my next step.
If you retain static pressure the car should start quickly. If system pressure remains overnight look to electronics.
A car with static pressure will start and run for 5+ seconds with no power to fuel pump(one time only).
Temp is not a factor, at least not a big one.
Other possibilities are leaking FPR (leaking into return line-not holding pressure), injectors dribbling into intake(usually rich at start), internal pressure line leak in tank (very hard to diagnose).
None of these would "get better" with a new pump.

Turbomack

I agree with Ninja as he beat me to similar thoughts. Question though: are you meaning priming delay (as typed) or do you mean priming duration? I’m using a different ECU (MAXX/Race) and have mine set at 3.0 sec duration and use a cranking fuel table based on coolant temp. Concur that your issues point to a FP issue and not fuel pump and wouldn’t come back to the fuel pump till I went thru Ninja’s checklist.

Ted75zcar

iTrader: (2)

When I went down this rabbit hole several years ago I came to the conclusion that these pumps do not hold pressure for any duration of time. I even went so far as to install a check valve on the pump side of things, which helped, but didn't prevent depressurization overnight. I have been monitoring FP for some time.

Side-note:
My 2003 nissan sentra suffers from the same thing. I have to prime it more than once if I leave it parked on an incline, head higher than tail.

DNMakinson

iTrader: (3)

I mean that the pump sees power for 1.5 seconds before the injectors are opened for how many mS I have programmed.

Thanks. If my present method remains consistent, I will leave it. All makes sense that pressure is leaking down, either through the check, or through the FPR. Since pump age and temp makes a difference, check valve seems logical. They may be better on the OEM pump. I thought I did not want to pay the Mazda price, but actually, I have, just piece-meal.

Turbomack

After a Walbro and 2 DW’s wasting a bunch of time and dyno money, I went with the Aeromotive 340 as recommended by my tuner. Problems went away immediately (i.e. too low of FP). If you had 2 bad pumps, the 3rd one just may not have the actual pressure/flow curve but can’t understand the tendency for it to happen in the fall.