Please help me diagnose a fuel problem...

[kswiss]

Okay... long story. Thanks so much in advance for any help you can offer. This car has been a pain in my side for over a year and its not even mine.

Car started having a misfire at freeway speeds and when under higher than normal load (up hills, accelleration.) It was rare, and not a huge problem. Took it to mazda, they said coil packs. Replaced them....

Same problem.

Started systematically replacing everything. New plugs, new coils and wires (like I said). New EGR valve. Found a random jacked up piece of wiring (missing some insulation and had been messed with at some point) going to the Camshaft Position Sensor, so I found a Mazda with the same engine at a wrecker and rebuilt that part of the wiring, and also bought a new CMP.

Still same problem.

I figure it has to be fuel, since its exhibiting symptoms of either injectors not firing or some fuel pressure problem, so I bought a fuel pump today.

Installed it....And the problem got worse!

Now it is practically undriveable. It sits there, nearly stalling out. I have to step on the gas to get it to rev or move in drive, and it pulses and then drops down.

Low fuel pressure?

Part of me is happy, because at least I did something that drastically changed the symptoms. I just don't see how replacing the fuel pump would make the problem worse, whatever it is.

Could i have installed the pump wrong? It's pretty straight forward.

One question I have is how the pressure between the pump and the fuel rail is kept high. The fuel line connection to the fuel pump seems flimsy....could this be my problem?

Thanks in advance again.

K

 

[P-Funk!]

Wow. I am puzzled. You need to put a pressure gauge on the fuel line to measure system fuel pressure (T it in).

 

[Dpwhitehead1]

did it ever throw codes? what codes??

is the fuel pump new?? the fact that it got worse tells me that either it's a bad part, or you installed it wrong.

 

[RABID_MP5]

hmm, the fuel pump is in a plastic body that hangs in the tank. It has an integral filter media in the body - that might be plugged. Was the tank clean inside and was the intake sock clean as well? If not I do suspect clogging. As for the pump changeout, did you replace the (expensive) rubber seal that the pump pushes into? If you re-use the old, it could leak internally, causing a pressure drop as well. That little seal is like 20 bucks. The whole housing/filter is only like 50 bucks with all its wires etc. You could stick in the old pump and help verify if it is better.

 

[kswiss]

Wow, thanks for the replies!

I pretty much swapped them straight out, but the pump came with an extra rubber piece, so maybe that is the seal....

The pump is brand new. Fuel tank is clean, and a new fuel sock.

It was throwing multiple random misfire codes before the change out.... but only in spots where a fuel pump would make its problems known. If I drove around on flat ground without gunning it, you wouldn't know there was a problem. As soon as a grade came, though...stalling. If it stalled too long....P0300 (or whatever the multiple random misfire is.)

I'll pull the pump out again tomorrow, and see what I can do about pulling the casing apart to make sure everything inside is as it should be.

Thanks again for the replies, I'll keep you posted.

 

[Dpwhitehead1]

could be the injectors being clogged.. random missfire codes often present when the coil pack is bad.

 

[ToNeZ90]

like they stated, possibly low pressure and injectors might have clogged.

I'm no mechanic though

 

[kswiss]

I have doubts about clogged injectors because the whole engine stalls like a fuel delivery problem....and it lasts for seconds at a time, then goes away.

It seems like an intermittent problem with fuel pressure, and then after I changed the pump, a constant problem with fuel pressure. (the second one I'm relatively sure of, because I didn't touch anything else. Also, no leaking or anything from around the pump.

It was cold today. Hopefully tomorrow the sun shines for a bit and I'll go pull it apart again and make sure I didn't install it wrong.

Thanks for the replies....is there a way to post pictures on here? And has anyone taken apart the casing for the fuel pump before? Some visual guidance would be helpful. If none are available, then I'll take some pictures tomorrow when I have it out for future reference.

Cheers.

 

[Dpwhitehead1]

there's a how to on the forum on installing a walbro. it might help you out. check the sticky on the main page.

and for pictures, get a photobucket account and then link the pictures.

 

[msp5]

What about the fuel pressure regulator.If thats stuck open there would be no pressure at the injectors, causing not enough gas to flow through the injectors.