I'd swear I'e read about a bunch of pressure related issues to the Aeromotive A1000 Pump in past but of course did some extensive google searches today & could'nt find anything worth reading....

Took my buddies '72 Challenger to track today & spent whole day chasing fuel system around, for second week in row...

Car was just finished last year late, & has a brand new A1000 on it, dual -10 Aeromotive inline filters(one before pump, one after pump), Aeromotive bypass regulator... It's I think off top of my head, -10 feed to reg, -8 bypass return... & we have a -4 gauge line running to an external non isolated 2 5/8 Autometer fuel press gauge on cowl... 16 gallon cell...This was an Aeromotive fuel system "kit" all from Aeromotive...

Put about 45 passes on it last fall, no issues... ran straight 110 Sunoco in it until last day of year @ a test & tune.... he was almost out of 110 & we cut in like 70/30 pump gas. Ran fine, put up new best yada yada...

Over the winter unbeknownst to me, he put a bottle of Sta-bil in the fuel, while his car sat in storage for 5 months...

We took it out first T&T this year, made one pass, air was killer -800 feet below DA, & ran 10.00 @ 136? Previous best was 9.87 @ 137 @ ~+600 DA... Incrementals were hair off, but that was on the old pump gas/110/sta-bil mix.... & had a leaking tube issue in slick & only got one pass. Also trans fluid, gear lube etc were nearly stone cold (36 degree day) So did'nt think much about it...Kind of just attributed it to cold car, cold track (60 sucked), & old fuel etc.

Next week, car still off a little, air was 2100-2400 feet DA all day (felt like August, not April), we started putting fresh 112 in it (all we had, waiting on drum of Q16 to come) & as the fresh 112 got in, car went quicker every pass... I think ended up going 10.08 @ 135.50 @ 2400 DA. So it looked pretty good, but 1/8 MPH was still hair off... then next pass 2100 DA, thing smokes like a diesel... & runs 10.18 @ 134... 104 in 1/8 horrible... Fuel pressure for no reason is now @ 9.5 PSI. We had it set last year @ 7.5 PSI & it had never moved, never varied... never worried about it. Hmm, so I adjusted it, took 4 turns on the adjuster to get it back down to ~7.25-7.5 range???? that's odd.... Made 1 last pass, loses 2nd round.... 10.05 @ 136. All good... MPH in 1/8 "normal" for 2100+ DA etc. Pass looked real clean....

Went back today.... & as he was loading/unloading car, fuel pressure all over place, from 5-9... depending on when you ran pump etc.

1st pass was slow again... like 10.14 @ 134, MPH in 1/8 was off by 2 1/2 MPH looked rich, he said did not check F press... I cleaned out air bleeds, dropped jet couple sizes, F press around 6.0 in pits... 10.08? 136, I put jetting back to 90 SQ where it has been for all year, backed that up with I think a 10.05 & then a 10.02 @ 136. Incrementals all look good now? Ok first pass was a fluke??? DA today was real consistent 1650-1700 all day. So think all is good... 1st round.... 10.12 @ 134, MPH in 1/8 way down... blowing black smoke... Float levels if anything are hair low....& I've adjusted them 3 times in last 2 weeks & really saw no differences in back to back passes, fuel pressure is varying wildy. Now reading low in pits around 4-5... I turn adjuster 1 turn & back to 7...

Buy back in.... 10.10 @ 135 black smoke, gets back to pits & says the F press was 9+ in lanes/burnout & down track... I'm lost. The adjuster is now 3 turns of of where it was last year (3 turns to LOWER pressure) & press as we loaded on trailer was 9.5 PSI...

We are going to drain cell tomorrow night, clean filters & pump, tear reg apart, flush all lines & hope we find something. ???

Hard to bracket race a car that throws out a wild slow pass every once in a while. We run alt on car, & also charge battery between rounds, so bat voltage should not be an issue.... Frustrating day of head scratching....

john from product engineering once told me that if your getting fuel pressure all over the place, its in the needle and seats and not the regulator. start at the carb 1st.

ive heard those isolators crap out on ya..

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ive heard those isolators crap out on ya..

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nonisolated

first thing i would do is go after the regulator. i assume the pump itself doesn't have any type of relief in it?

another odd possibility would be something plugging the return line. maybe a sliver of hose liner if someone wasn't careful assembling the hose ends. failed regulator and/or trash in the system would be most likely.

if you're referring to the isolator ruining the pump i don't know how it could. that said the isolators are imho no good just from basic design and i've never seen one work properly. it requires the line from the isolator to gauge to be hydraulically stacked in order to work. problem is the fuel pressure will vary due to unavoidable thermal expansion and contraction of the fluid in the isolator, line and gauge. he mentions that the gauge system on this doesn't have a isolator.

Had the same problem with mine.Had to adjust it up to get it up to 6.5 The adjuster is now flush with the lock nut.pressure bounces around coming through the traps.Let me know what you come up with.I was going to replace the diaphram in the regulator.Also mine is pump gas and runs the same as yours.Same pump.No bypass line.Let me know

james i was talking about cutting the line and debris getting all in there.....

My fuel pressure was all over the place when I first brought out my car last year. What finally fixed the regulator was putting it on shock mounts held steady after that. Also sounds like the Sta-bil is screwing up the regulator and carb.
Lets us know if you find anything.

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problem is the fuel pressure will vary due to unavoidable thermal expansion and contraction of the fluid in the isolator, line and gauge

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As an aside here - we reduced that problem significantly by using Dot 5 - silicone brake fluid.

Sounds like cavation to me. Tell us more about the before and after filters. Are they the same or are they the 100 micron before the pump and 10 or 40 micron after the pump?

Is the fuel pressure gauge liquid filled?

As for isolators IMO they are very slow to react so if there is an issue like running out of fuel pressure you wil likely never know.

I'll ask tonight how much Sta-bil he put in, although I doubt he will remember & knowing him, he probably dumped in the whole bottle without even thinking.

The gauge is not a liquid filled one & it is external mount on the cowl, so no isolator needed.

It has the aeromotive inline -10 filters that came with the "kit" before & after the pump, I'll have them apart tonight to see what they are exactly, micron wise.

& I will replace the needles/seats tonight as well, that was something I had'nt thought of, although float level in pits never seems to vary at all.

System worked fine all last year, something just got into it over winter & it now has gremlins....

If it is of any consequence, I have cars that sit for long periods of time. I have found that the o-rings on the Holley needle and seats can disintegrate whilst sitting. Just something to check.

I had nothing but problems using an A1000 on a fuel injected application. Finally switched over to another brand pump and problem solved. However, mine never worked at all.

I would swap the an-8 return with the an-10 feed.
most regulators like a larger return line.

Second I would remove the filter before the pump.
may cause cavitation. leave the filter after the pump.

We have s similar problem, each time you turn on the fuel pump we get a different reading 6-9-7-10, damm thing seems to have a mind of its own, I have turned the reg pressure down 3 turns and still get funky readings, all was fine last fall, just ordered a new reg hope thats the fix

Oh oh, I hope Aeromotive pumps are not getting a bad rap all of a sudden, I just received one in the mail as part of my in tank fuel system.