So I'm driving around the area and *jiggle jiggle jiggle* car starts to buckle. Ok that was weird. She didn't turn off just bucked like a wild horse at a rodeo show. It didn't do it again that night.

A few weeks later it happens again. But it's weird cuz it will only happen once in a blue boom. Finally, it started occuring intermittently. I noticed the fuel pressure gauge was going from normal pressure to 0 then back up to normal pressure again.

Now I know it was only 1 of several things:
1) Fuel Pump
2) Fuel pump resistor
3) Fuel pump & circuit relays

Went home and it starting bucking again. Got it in the garage turned her off and thought...hmm...let me try to start her back up. No fuel pressure. I'd turn the ignition on and off and sometime's the system would prime itself and sometimes it wouldn't. Ok, well this kinda makes it easy to diagnose

First step was check the fuel pump & circuit relays. To my surprise, the fuel pump relay would engage but not allow current to go through.

Bad relay

I checked the omhs on the resistor and pump just to be on the safe side and both were within spec (as per factory manual). So.......... I removed the fuel pump relay and replaced it with a direct wire to ensure that the relay really IS bad. Went out for a drive, and no more bucking

I can't believe that stupid little relay is $75

 

excellent write up. i had a similar problem with my daily driver. i had to take it to a shop and pay $150 to get it fixed. wish i saw this eariler.
anyone else think this is archive worthy?
got my vote

 

Hmmmm this situation makes me want to go out and replace mine just for the hell of it. No fuel under boost means by by engine.

 

Good reason to have a fuel pressure gauge. I have been meaning to put one in, hopefully this winter. That fuel system is so darn touchy

 

Hey Flybye where u getting on the gas the time it happen? Or normal driving conditions? Khris

 

WOW! That sounds like detonation. It was under boost? Were you steping on the gas at that time? Are your seals ok?

 

Good diagnosis! That's why I've had a FP gauge on order for 3 months (damn Defi!).

I had a supercharged miata do the same thing, and the FP gauge helped catch a weak fuel pump. For the record, the A/F meter (non-wideband) would go complete lean during the bucking as well... They're not accurate enough (well, the sensors anyway) to tune with, but they're great for diagnosing hiccups.

 

I was lucky enough for it to only happen while cruising, but damn it felt like I hit a brick wall

18-19 of vacuum and still going stong

My fuel pressure gauge was the FD's 3rd mod. Lack of fuel is our biggest enemy, so why not keep an eye on it?

I've learned a lot of neat things with the gauge like
1)Pump DOES prime the fuel system before cranking the engine. If engine doesnt start up, you will at least know first hand if you are getting fuel or not.

2)The pump certainly works at a lower speed during vacuum and under 5spi of boost

3)At about 4-5psi of boost, fuel pressure instantly rises from 40 to about 50psi and continues to rise. On cool days reaching 13+psi of boost, I've had almost 60psi of fuel pressure.

4)It's the perfect diagnostic tool for the fuel pressure regulator. If you prime the fuel system, and pressure quickly drops down to 0, then you know you either have a bad pump or bad regulator.