Changed fuel filter RB20DET, now runs like dog%%$#!?!?!?!

[kumasan616]

I'm stumped I thought I would ask opinions... so I decided to change the fuel filter on my RB20DET. Picked up a KA fuel filter (closest match). Disconnected fuel lines leading into fuel filter/out to fuel rail. normal installation. Go to fire it back up and it barely sputters, pops/backfires, does not want to run. I changed the original fuel filter back, and it is still doing the same thing. I'm baffled...1. Fuel Filter is installed the right direction (In/Out is correct)2. fuel pump is working3. no vacuum leaks or bad sensors, getting a code 55 (all good)

Any ideas?
Modified by kumasan616 at 4:53 AM 2/7/2009

[toadx8u]

why on earth did you get a KA filter....everyone knows when you do the RB swap you install a z32 fuel filter go back to the store and buy one for a z32...the KA one is too restrictive

[kumasan616]

odd... the Z32 filter I checked at the store didn't match up at all. Okay well I'll take it back for another one.

What stumps me is after trying the new filter and failed, I put the original filter back on and it did the same thing...?

[Carl H]

you are kidding right...they flow the same, i have a ka filter on my vh45de s13 coupe...only reason you'd go with the z32 is for larger filteration.

why on earth did you get a KA filter....everyone knows when you do the RB swap you install a z32 fuel filter go back to the store and buy one for a z32...the KA one is too restrictive

did you by chance mix up the fuel lines?

[Coolwhip]

Z32 TT fuel filter, it'll work, and is the way to go.

The reason why your used filter was doing "alright" was that it wasn't filtering probably, haha.

[kumasan616]

lol sadly it wasn't doing "alright" they both had the same response (engine barely trying to run with throttle open, backfire/pop/sputter.I am pretty sure I have the fuel lines hooked up properly. Here is how I have it hooked up:

1. line into filter (round part)2. line out of filter (flat top part) into lower fuel line3. fuel line leading away from pressure regulator (upper line) back to return line

I tried the other way thinking I somehow screwed this up and the fuel pump bogs down with pressure as it hits against the regulator in reverse...

[DrifterProdigy85]

Is it possible the Fuel Pressure has changed causing it to run too lean or rich?

[Carl H]

or better yet what fuel pump is in the tank?

[kumasan616]

its a stock fuel pump (remember the car is a C33 laurel that came with a RB20DET stock) and I have not yet checked fuel pressure. Would the ECU adjust for added fuel pressure?

[mattblancarte]

Z32 TT fuel filter, it'll work, and is the way to go..

I slapped one on my 26 and it works great.

[Carl H]

it sounds like the fuel pump has gone south...proly due to contaminated gas or just old age.throw an inline gauge on there and see what it does...if pressure drops when throttle is opened then its either the pump or the regulator...pump is my bet.

[kumasan616]

Sounds like the pump is working fine, it primes nice and strong... I'm going to check in line pressure maybe its not producing enough pressure under running load...

[USMCgetsome]

the pump is a likely cause. Mine ran fine at idle but when on load it would sputter/pop/and just be flat in the rpm range. Then it would come on strong as it should after a sec or 2. took awhile to figure that one out.

[Carl H]

sounds like and working properly are two different things...i had a q45 pump that SOUNDED like it was working but pressure would drop like a brick the moment load was applied.

[SullivanRacing06]

check fuel pressure, get a z32 tt filter, and ya know a walbro 255 pump is under a 100usd, good time to upgrade

[kumasan616]

okay new filter is in (used the KA filter, flows fine)checked fuel pressure, 50 psi key on, 45 psi cranking, 43-45 psi running and pump is strong, so fuel pump is all good

checked throttle blade, it was stuck open about 25% thanks to a binding throttle cable, after fixed still didn't solve problem

runs lean, idle is near stalling (cold), occasional popping (although much better now), and if the throttle is touched it surges MUCH higher than intended, stays there, then almost dies, all while running lean. Onece after blipping the throttle the car jumped up to like 6K for like 2-3 seconds, then died. VERY odd. Next I'm thinking test the fuel pressure regulator, then if its not that, I'm going to pull the injectors to see the condition/clean (may have gotten clogged) and check plugs to verify condition

Still convinced its a fuel delivery problem...

[240z4u]

Is that fuel pressure with the vac line off the FPR? If its not, its set too high. 38 with line on is closer. 43 line off while running at idle is correct.

Evan

[Kansei240sx]

Use some vice grips or hose grips and clamp off your return line, see how it runs then.

[kumasan616]

Evan-line was off during test, so fuel pressure looks good.

I pulled the fuel injectors/rail/etc.... discovered moderate green corrosion on the terminals for the #3 injector (and with the green crap measured no ohms due to connection issues), and a little corrosion on the rest of the injectors. Cleaned up all the contacts, measured ohm resistance, all about 14.3 after cleaning up the contacts. The filter screen on the #1 injector had a hole in it, but life goes on. Cleaned out the injectors as best I could using starter fluid. Also, the IACV (NOT the AAC valve on the back of the intake manifold) had corrosion and a pretty busted-up looking connector. Cleaned up the contacts and get the plug zip tied in there (connectivity is good). Have not test-fired it yet (due to late night working + sleeping kids)... stay tuned, hopefully the problem boils down to corrosion on electrical contacts...

[kumasan616]

dammit, no luck... after getting everything cleaned up and reinstalled, same crappy conditions. Starts up, very low/rough idle, then it sounds like its slowly loading up (idle slowly creeps up), then suddenly it surges up to like 5K, then drops way down.

I unplugged the AAC, the idle surges up and down ~4K like it has a bad TPS, only worse...

Could clogged/stuck open injectors cause idle to suddenly spike like that? I'm going ot replace the fuel pressure regulator, maybe that one went south... hopefully I don't have to change out the injectors for new ones, these can be pricey...

Oh and I am fairly certain I do not have any vacuum leaks, all hoses look good and are securely connected
Modified by kumasan616 at 11:31 PM 12/15/2008

[kumasan616]

...and it runs! Kind of... well I had my stock injectors rebuilt by RC Engineering, they were great, came with a flow test sheet with before/after stats.

I adjusted the throttle cable a bunch more and it took care of the problem for the most part.

so now I'm down to figuring out what is causing my engine to stumble/die on initial fire up, and needs throttle input for regaining idle when cold, and runs lean with a slight miss when warm... I changed out the fuel pressure regulator, regapped plugs to 0.8mm, coated the coil packs with high temp rubberized tool coating, new Q45 TPS, and no luck...

Next is... a Walbro pump. the only question I have is, will the extra fuel pressure from the pump require an adjustable regulator?
Modified by kumasan616 at 5:10 PM 2/3/2009

[Sil240]

Yeah with the Walbro, your going to run richer at idle. Don't know about the rest of the RPM band though.

You should pick up a Nismo AFPR easy to install. You don't need any lines or fittings.

[USMCgetsome]

have u changed out that coolant temp sensor yet?

[kumasan616]

yup, dropped in a z32 one, same result... funny though, when I unplug the sensor, the idle instantly goes up and smooth, regardless of which WTS I am using

[Sil240]

Maybe you have a short in your wiring?

[kumasan616]

I think I have it... tried the above suggestion, about clamping/restricting the return line, and it ran smooth! I think its the fuel pump. I ordered a walbrother unit w/ install kit for an S13, I'll report back once installed
Modified by kumasan616 at 12:34 AM 2/5/2009

[kumasan616]

holy crap, after a year of gremlins, it FINALLY runs! Well I swapped out the fuel pump for a walbro unit last night, produces a solid 40 PSI, so that was good. Still stumbling... so I left it last night with a battery charger (cranking slowly). Came out in the morning, still acting funny, but I let it warm up, tested timing, it was spot on. Next I grabbed a probe light and back-probed each coil pack, and sure enough, #2 was crapped out! I swapped it for a spare I had, let it cool down, and cranked it again. BOOM! Strong idle, very rare misfire (could be another coil pack slowly dying) but otherwise runs strong! Thanks to the local rain we had, driving it around the block was a slippery and fun experience. Scared an old lady as I slid past her corner house as she was coming out to grab a newspaper... lol

I decided to drive it over to Garage Boso to show it to a couple of buddies, ran strong, and got a lot of thumbs up from Ross and the guys.

Thank you to everyone for your help!