Hi, working on a 2003 Santa Fe, AWD, 2.7L, has a low rpm miss, and some driveability issues. I'm leaning towards failing fuel pump, as the symptoms don't really change as the engine warms, which leads me to believe it's not a one of the ten cats. Anyway, I can't find anywhere to test the fuel pressure. No fuel filter, no schrader valve, and the only fuel line that comes apart so you could hook the gauge up to is is the return line, just tank side of the regulator. Do you need some kind of fancy adapter? Or am I on crack and missing something. I really don't want to spend 250 on a fuel pump and still be staring at the same problem with an empty wallet. Thanks for any help, I really appreciate it.

 

Scan first, low fuel pressure will not give a single cylinder misfire, it will be BLAAAAAH from not enough fuel to make power..

You can test pressure, just need the Hyundai adapter to tap into the pressure line.

Plugs (NGK Platinum or IRIDIUM) and a set of new wires will likely cure the problem if near orover 60,000 and never been replaced.

 

Thanks for the reply. It gives off a P0303 code. The Santa Fe has 185,000 on it, about 5k and six months ago I put on NGK plugs and new wires, air filter, pcv etc, it's been gradually getting worse since for about a year. I compression tested it and it came out good, can't remember for sure maybe 130 or so, so i bought a new injector for cyl 3. No change. I found the pressure tester adapter on otc's website, but don't really wanna spend 90 to use it once. I originally thought it was the upper cat on the rear bank, and the misfire was because the exhaust for cyl 3 went directly into the cat, and it was giving it too much backpressure. Just for giggles I replaced the upper o2 sensor in that cat, and no change. I'm down to either cats or fuel pressure. Since no 3 is almost at the end of the fuel rail, I figured it'd be succeptible to low pressure, but who knows.

 

Guessing at stuff gonna get expensive..

 

[SARCASM]

But not as expensive as it would be to take it to a STEALership mechanic to get it fixed properly.

[/SARCASM]

 

Thanks for all the input, it's much appreciated, as I don't have much experience with Hyundais.
I tried switching the wires and plugs.
I know I should have moved the injector too, but after I checked the compression and everything else seemed ok, I was relatively certain that was the problem.
I didn't switch the O2 sensors, I bought a new upper, I know they have never been changed, so they're overdue anyway.
The engine misses at idle, and is sluggish on take off, even just revving it up in park, and sometimes backfires/pre-ignites as you're taking off from a stop sign. It does reach highway speed, but it is short on power. Even under load around 3k, say going up a longer hill at 40mph, it'll stumble.

 

I'm not opposed to taking stuff to Mr. Hyundai, but at this point I'm only out 48.88 plus tax for the injector for stuff that wasn't overdue to be replaced anyway, and I enjoy the work.

 

And compunding your troubles so deep it will take somebody a good bit to unscrew what you did to make sure all the other stuff is ok before we can proceed with actual concern.

 

I guess I can put the original O2 sensor back in if that'll help. Otherwise, I'm here looking for advice from someone who knows more than I do. At this point my symptoms have not changed since I did any of the work, which leads me to believe I haven't f'd anything up.

 

I was able to rig up a gadget to check the fuel pressure at the pump, just using a male and female of a 3/8 quick disconnect and some 3/8 hose to my gauge. Pressure was 37psi running, 48 psi running with regulator disconnected. Seems to be in line with the specs that I've found.