Weird fuel pump issue

[Sirnixalot]

I just got done doing a full rebuild. Before the car did not have any fuel pump issues (other than a loud as hell walbro).

The car has a rewired Aeromotive Stealth in tank pump in it now, i have 12ga wire running directly from the battery in the trunk and i am using the pigtail that comes with the pump connected directly to the 12ga wire bypassing the stock connector. The tank is full of fresh 93 octane.

If i start the car and let it idle the pump will be nearly silent (i do not have the back seats in) and if i drive the car then everything is normal.

The problem comes in shortly afterwards.

When its just idling i can hear the pitch of the fuel pump change and if i go and rev the car and watch the fuel pressure gauge the fuel pressure dips instead of increasing. If i disconnect and reconnect the pump quickly while its running sometimes i can get the pump to go back to the near silent whine.

When i am driving and it happens i can drive around in vacuum just fine but as soon as i try to go into boost it pegs lean (obviously)

During the rebuild i relocated the alternator to the rear of the block ala the Jays Racing relocation kit. I extended the alternator voltage wires and have a 4ga ground to the firewall.

I have reused the stock 6ga ground wire that goes from one of the starter bolt's to the frame. The battery has a 4ga ground to the "nut" used to hold the spare tire down.

The voltage from the battery is 12.4V (i know its a little low). If i disconnect the battery while the car is running and measure the voltage using the batterys ground wire and the positive battery wire in the trunk i get 13.7v.

Sorry for the essay but i am really out of options.

 

[Sirnixalot]

The plastic thing that joins the return line with the hose that draws fuel from the passenger side of the tank has been damaged so i replaced that with a T and ran the extra hose outside of the stock fuel tank sump so it would not aerate the fuel in the sump area. If this is my problem i have no idea.

AEM FPR is using the smallest return restrictor. I disconnected the return line at the tank and fuel was happily ****ing away. Fuel pressure is set to some where around 42-45psi. It will stay there all day long until the pump is asked to flow any volume then dips to 20psi.

Tried disconnecting the alternator to see if that was the problem. The pump got remarkably quiet (i guess 12.4v will do that) and the noise did not change but still the pressure dipped whenever i would rev the car. Negative results

Tried adding resistance to the circuit. Negative results. (no idea why that would work but I am desperate)

Fuel filter in the engine bay is clean

If there was a way for me to see if it is emptying the stock sump too quickly i would love it (but its on a full tank of fuel so that makes no sense).

I am convinced there is a ****ing midget gremlin that is treating my fuel tank like a jacuzzi and hitting the bubble button after he settles in.

Taking the car to some local evo experts and seeing if they can fix it.

 

[turboglenn]

I never trust that junction at the pump to hanger with the o-ring and other parts from OEM or that come with the 255 pump

what i do is this.. Take a piece of fuel line that's a smooth but snug fit (i personally use a short piece of pushlock style -6 an hose - the lue stuff i can get a pic if needed) I remove the o-ring,spacer and crap and toss them out.

Stick the blue hose over the pumps oulet and push all the way down.

Trim fuel line/blue push lock hose to where the "head" of the outlet is the only part sticking out of hose

secure hose to outlet with small hose clamp

Now, stick the pump with the new hose piece as it's seal up in the hanger, it will be a tough push, i lube the hose first with spit or WD-40 or similar and twist and push in (it should be a damn tight fit)

Then secure the pump with your choice of ways.. I use a hose clamp since my pumps always have their sock in a different location than the OEM pumps, and i just put the lower part that is held in with the screw in the drawer in case i need it sometime (piece that goes under pump - it's part of the OEM hanger) if using a hoe clamp to secure the pump, be smart about how tight you go..use enough to hold it, but don't crank it to all the clamp will give you, i'mnot sure it would damage the workings of the pump but why risk almost 100 bucks on it???


I"ve tested this to the point of the 255HP's reliefe valve opening or the psi my AFPR will let me hit max for base presssure (around 85psi)..

See, i have always ran into this same issue when doing it by the book for wally installs, (my last tank for FWD had a custom hanger i built and now sold) but anyway, on my AWD swap, tried OEM and intsall kit and got same thing. let itidle and turned scrwe on AFPR and it hit like 40 and then dropped to 20 and wouldn't go higher..checked and the o-ring was deformed andhalf blown out. So, I quickly grabbed a piece of blue push lock and a clamp and viola, was able to make 85psi base by turning screw on AFPR at idle.. dialed my AFPR back to 43psi base, hooked up vac line and haven't had a single issue yet...the blue hose just acts as a large long o-ring thats' a tight ass fit and hasn't let me down or degraded under E85 submersion at all (i worry about plain black fuel tubing from parts stores maybe softening up and droppingpressure on me at a bad time but i'm sure its fine = i'm paranoid )

 

[bryanwheat]

I agree also to check the o ring on the pump. If it is bleeding off the pressure in the tank than i can easily see if causing an issue like this. IT will also cause the pump to be quieter because there is less of a load on it. I would also back probe the fuel pump connector plug with a multimeter and go for a drive and watch fuel pump voltage.

 

[Sirnixalot]

Thanks for the info guys

I went a step further last night. I cut that cup shit off and welded a piece of tube on there so now its 8mm hose clamped on to both and its leak free.

I checked the fuel filter again and there was some small things caught up by it but nothing that would have blocked it. I am using one of the small filters from summit. Maybe i need to use a larger filter?

When i initially started the car the fuel pressure would drop when the motor was revved. I disconnected the feed line from the rail, and cranked a few times to get any air out of the line and reconnected it. Started the car and voila good fuel pressure.

On the drive from my moms house where all my tools are to my apartment (15minles or so) the issue came back after about 10 miles of driving but i turned the car off and started it back it went away.

I am not sure if it is the filter i am using or if i need to step up the return restrictor to a larger one?

 

[Sirnixalot]

still fighting with this, i think another pump is dead. It is now pointing to being a voltage issue since the regulator is working as it is supposed to. That being said i have a Fuelab 535 regulator on the way.

I tossed the old factory 6ga ground in the engine bay and ran:
One new 4ga cable from the starter bolt to the frame
Two 4ga cables from the alternator to the inside of the firewall and to the outside of the firewall
One from a coil pack mounting bolt to the outside of the fire wall
I replaced the ground i had for the battery in the trunk, it is grounded to the spare tire securing captive nut.

I sandpapered all the paint off where the terminals made contact on the car as well as the under side of the bolt heads where required (used some new bolts)

Result is 14.2V at the battery in the trunk at idle. I did NOT change the 12ga wiring to the fuel pump yet. I am getting 13.78v at idle at the fuel pump, not that it ••••ing mattered.

I do not know if the damage is already done to the pump or what but i just can't afford to keep buying pumps so i don't know what to do.

I doubt it is injector related because the car would boost just fine when the pump would work.

At this point i am trying to find another car to test this pump in so i KNOW it's bad and then get ANOTHER pump if it is.

I am also picking up some new 10ga wire to replace the 12ga i have going to the fuel pump and a bigger soldering iron to solder instead of using crimp terminals since there appears to be a voltage drop between the pump and the battery.

 

[turboglenn]

I would bet on that aeromotive pump being the failure, i'd trust a wally before the aero in most cases, especially where they see high fuel pressure with boost. In my experience the aeromotives i've been around seem to do well at lower static pressures but seem to give out when pushed into higher psi ranges, plus they are really picky about being run where they can't pick up fuel and not working again afterwards (at least in the fwe i've dealt with, we replaced 3 on one car all in a row in less than a month)

 

[Sirnixalot]

Thanks for the insight all the same

Just to recap

No leaks from pump inlet all the way back to the return to the tanke
Fuel pressure regulator is operating as it should
Fuel tank vent is not blocked, running without the filler cap does not change anything
Fuel filter is not blocked
Voltage to pump was "low" 12.4v, it is now 13.8v which still shows a voltage drop of 0.5v from the battery
Ground's were lacking resulting in a 1.6-1.9v drop between the alternator and battery

Fuel system consists of:
Limping Aeromotive Stealth 340 pump (rewired)
Stock hard feed and return lines going to the engine bay
Metrick to -6AN adapter to -6AN small Summit fuel filter
-6AN push lock line to the stock rail with -6AN Male bungs welded to it
-6AN push lock to the AEM FPR with the smallest return restrictor
-4AN push lock return (same size as stock) from FPR to hard line in engine bay
FIC 750cc injectors (working)

 

[turboglenn]

So, have you resolved the issue then? In your very last post it sounds like you're saying you've figured it out but in stating the fuel pump is "limping" are you implying that the pressure is still low?

You could always toss the old wally back in and see if your problem dissapears. even voltages as low as 11.0 v flat wouldn't be bad enough to cause a lack of fuel flow under normal driving conditions, at least not enough to make the car lose pressure at higher RPM's when there';s no boost involved.

The OEM mitsu alternator is crap too, and the higher you rev them the less volts they tend to produce both overtime as a whole and under immediate observation, but with all the issues i've seen with them a good ole walbro pump was doing its job until i got into areas where i needed to be maxing out injectors of the 720-1000cc/min range.

Having replaced my alt with the saturn model and wiring it up according to my post in the custom fab area "important imp[rovements to saturn alt swap" I now have near perfect voltage at all times to the pump and everything else. I'm seeing roughly 14.4-14.6 at the ECU (read via datalogs) withno accessories on, and with everything running and the engine at least above 900RPM (due to pulley size and minimum rpm of alt needed not matching perfect when adapted to our cars) I'm seeing anywhere from 13.4 to 13.8v during 1000 RPM idle and normal cruise conditions

My fuel pump is fed via 10 gauge wire from a distribution block on the pasenger strut tower that's fed from the battery via 6 gauge audio amp wire.

pressure is a function of volume and restriction equalling force, if you have the proper volume you'll build the force, but you need a certain amount of force from the pump in the form of energy exerted from proper voltage to move that volume to the filter and AFPR where you adjust and build the desired pressure.. if pressure falls off then you are dealig with a matter of lost volume plain and simple, which would be either a restriction in the line/filter or leak in the system some where. Are your clamps tight at the new internal hookup from the pump to the pump hanger? reember 40-75psi is quite a bit, so nothing less than some small hose clamps will do the job, certainly don't trust it to zippy ties

 

[Sirnixalot]

I can try removing the fuel filter element and see if that is the restriction. I have run the pump and the filter without it connected to the rail and fuel comes out as expected but i don't know what x CC's of flow and y psi of pressure looks like with it just pouring into a gas container.

I have cut the retarded O-ring cup that the fuel pump outlet fits into from the fuel pump hanger and welded on a steel barb in its place. I tested the welds with spay water and air and they were good but as a precaution i slathered some JB weld over them anyway. I am using about 2" of 5/16" hose and 2 hose clamps. No leaks there.

 

[turboglenn]

well, what you can't test is how the pump flows under pressure, the only way to test it is going to be to swap out another one and see what it does, you've already shown the first signs of it not flowing, might as well back up theory with a control group fuel pump (old walbro you had in there) and see if it's acting normal. if it's fine with teh walbro you know it's the pump. if it's not and does the same thing you know to look else where., Doing anything else at this point is just wasting time dancing around finding out the real problem

 

[Sirnixalot]

Fuel problem fixed.....the fuel filter was blocked solid FACE-EFFING-PALM

The $30 summit/russell etc fuel filters are not enough when you have had the tank sitting for a while. Don't cheap out, get that Klushman or Fuelab $90 filter!

So about that, as i go to start it back up after cleaning the small filter disc it looks like a rod bearing went. Plan is to pull the oil pan this weekend and see what went exactly and decide a plan of action from there. I don't really trust the cut crank in there now and am of the mind to just fork out for a new rotating assembly which sucks.

I have just had bad luck with the used short block i bought on here a while back, first one of the bores come scored so i ordered new rings and bearings (clearances plasti-gauged good) only to run into this shit 250miles in.