Runs Terrible with Load - Low Fuel PSI

[Ajwit87]

Heres my deal this time guys. Mods are listed in profile, but not really relevant to this problem. I had some boost leaks before and a horribly running car, it would start and idle just fine, but under boost it would fall flat on its face.

No more boost leaks, good compression (155) in all cylinders. Brand new NGK BPR6ES plugs and NGK Blue wires. Boost controller turned all the way down since I run so bad near boost. Or specifically, anything near no vacuum/0 psi. So basically the more air im pushing, the worse it runs.

Today, I did a fuel pressure test, Im only seeing 33-34 psi at the fuel filter. Next, I took the vacuum line off of the Fuel Pressure Regulator (FPR), no change. Then I pinched off the rubber return-line, no change. So that rules out a FPR.

Next suspect, fuel filter, it was removed and cleaned off. You can blow air through it with just your lungs with no air flow loss. Then i even blew compressed air through it with the same result. All of our Master ASE techs agreed the filter is not the culprit.

All of this points to a bad fuel pump, which im preparing to purchase and install tomorrow. I will obviously be looking for leaks and pinched lines near the tank during removal.
I couldnt imagine a stuck open injector doing this. My narrowband A/F gauge is always pegged lean with any throttle, bounces at idle, BUT, my plugs when I pull them always smell like fuel.

My question is simply this, do you think I am forgetting about something here? Could it be something other than a bad fuel pump or pinch/leak in a line? I just really cant afford to buy a pump and be wrong here. Thanks.

 

[BogusSVO]

Check voltage to the fuel pump, maybe try the DSM fuel pump rewire before swapping pumps

Low voltage to the fuel pump will not the fuel pump spin like it should to make pressures needed.

 

[Ajwit87]

Could I just run a straight 12volt battery wire to it? If so, do you know where the easiest place is to splice your wire into? ie, like just use a t-pin on the wire near the tank, or should i lower the tank.
Ill perform the test tomorrow when I have access to a lift, should I be close to 12 volts, or does this pump run 9v?
Thanks.

 

[BogusSVO]

I would use a volt meter and check it outside the tank, I think there is an acess panel in the hatch??

I would think 12v like everything else in the car, if you see 9v I would say thats your issue.

If you hot wire it, then check the fuel pressure and see if it went up.

The car is not new or even just 5 years old, so the power wire to the pump may have built up a ristance, or a bad ground.

 

[Ajwit87]

Ill do both of those things tomorrow. Im still going to get the pump transferred over from Advance, ill return it if it is the wires. But at least this way ill have one ready if its not. Thank for the advice.

 

[BogusSVO]

If its the pump, insted of the parts store replacemnt, check with supporting vendors for a Walbro 190 or if money allows the Walbro 225 and AFPR kit

May take a few days to get, but will allow you room to grow.

Here is a link to a feul pump rewire
http://www.dsmtuners.com/forums/articles-electrical-wiring/211560-alternative-fuel-pump-rewire.html

 

[Ajwit87]

Thanks for the link. Im actually keeping this one more on the side of a reliable driver. So no need for a walbro. Im looking into a pump that has 160lph, which i believe is similar to an evo 8 pump. Thanks again.

Oh, I forgot to ask. Would that fuel pressure reading be the reason why Im running so terribly. I mean so bad that I cant really drive the car. It starts and idles, but any throttle and it bogs a bit. Once i let the clutch out, its fighting just to stay running. I had to have it towed a mile back to the shop.

 

[danielbo91]

You actually you wrong that the evo8 pushes 160lp it actually pushes 190lp just like the walbro 190lp with im runing and is alway better than that stocker fuel pump

 

[Ajwit87]

Thanks for that daniel, but im looking for help right now about my low pressure. Not too interested in actual 190 vs. 160 pumps. Again, a stock pump would do me just fine.

 

[brian102]

Yeah you dont have to drop tank pull the two little tabs under back seat. Whole seat comes out and the access panel is right there.

 

[Ajwit87]

Thanks brian, should I look up a wiring diagram or do you know which wire is which and what readings I should be getting?

 

[Calan]

Today, I did a fuel pressure test, Im only seeing 33-34 psi at the fuel filter.

How did you test the pressure?

 

[Ajwit87]

I used a professional fuel pressure test kit, it had a longer bango bolt that replaced the one that goes on the top of the filter, so as you can start and run the car with it hooked up. The way its tested, it has a quick connect port on the head of that bolt which you connect the fuel gauge that comes with the kit to.

As mentioned, whether the vacuum hose was on or off the FPR, it did not matter. Pressure held at that number, even with the return line being pinched with pliers. If i revved it up, a very slight pressure drop, maybe 2 psi occured.

 

[Calan]

As mentioned, whether the vacuum hose was on or off the FPR, it did not matter. Pressure held at that number, even with the return line being pinched with pliers. If i revved it up, a very slight pressure drop, maybe 2 psi occured.

That is very strange. Sounds like your AFPR isn't doing anything to regulate the fuel pressure.

 

[BogusSVO]

If the FPR had failed, he would see 70-90 psi fuel pressuer, Of the fuel pump was putting out proper pressure.

The fuel pump has to put out more prusser than needed.

 

[O HAI]

sounds like a fuel pump dying or not getting the correct voltage. walbro 190 might be cheaper than a stock replacement depending on where you get each of them from

 

[Ajwit87]

I agree that it is strange, im getting 38 psi today, and that reading is again, not affected by the vacuum hose on the regulator nor pinching the return line. It is affected slightly by an increse in rpm.

Regardless though, Im lucky enough to have the best diagnostics guy in western PA at my assistance today, after looking at an ignition scope, I have a lean misfire in all cylinders while performing a snap throttle test. Then, with the MAF unplugged, smoother sound and way better looking waveform on the snap test. I need a new MAF. Luckily i have an extra in my basement, not sure of its working condition but its worth a shot before I buy one. Ill update after I install the new MAF later today.

 

[BogusSVO]

one last quick check..... with the vac line to the FPR unhooked cycle the fuel pump a few times and see if fuel spurts out of the vac line of the FPR

 

[Ajwit87]

When you say cycle the fuel pump, that would mean starting the car. I have no prime in this car, only when cranking and running do I have fuel pressure. No visible signs of fuel in vac lines though.

Great, the other maf I had is worse than the one in the car. Back to the original one. I need to find one local, this sucks.

 

[BogusSVO]

Bypass the FP relay or just cycle the key a few times.

What you are looking for is a bad FPR a rip in the diapram.

 

[bryanwheat]

If there is no change with the line unhooked than i'd suspect a problem with the regulator. It should raise with the line unhooked.

 

[BogusSVO]

I did a fuel pressure test, Im only seeing 33-34 psi at the fuel filter. Next, I took the vacuum line off of the Fuel Pressure Regulator (FPR), no change. Then I pinched off the rubber return-line, no change. So that rules out a FPR.

bryanwheat... He pinched off the return line with no pressure increase, stock pressure on a DSm is appox 40-43 psi, or in that neighborhood.

If the fuel pump is not making that much pressure, then the pump is weak or is not reciving proper voltage so the pump can spin and make the pressure needed.

 

[bryanwheat]

I didn't see that he pinched the return line. I would suspect the o-ring that seals the pump to the housing if that is the case. Could be a weak pump, but i would assume that it would still raise the pressure some by clamping the return line down.

 

[BogusSVO]

It also could be the hose between the pump and hanger

 

[bryanwheat]

There is no hose, the pump has an o ring on the end with a plastic retainer and it slides into the fuel pipe on the sending unit.