89 Turbo runs better with one fuel relay out?

[1986911]

A few weeks ago my car died and it was the fuel pump fuse. Swapped in a new fuse and its perfect. Right before it died, I noticed the rpm's creeping up a few hundred rpm. I got home, replaced all the fuses with new ones and car was ok. After that I drove it around and had the same issue with the rpm creeping up as the car warmed up. Did the standard check for air\vacuum leaks and replaced both fuel pump relays. Car ran perfect for a while.

Now I install my new WEGO AFM from our host and check my AFR and they seemed a little lean, I tweak the fuel less than a quarter turn and done. I thought finally its perfect. Odd as a few months ago car was dyno tuned with a new BL adjustable wur.

Now a few days ago after a warm restart I notice my afr on idle is around 10.2 down from the usual 13.7. Car still ran strong and the burble on decel disappeared.

I start it up today to check on it and its fine. 11.5 at start up then rising to mid 13's as it warms up. I shut it off and bam! 10.2 again????????

I go to the fuse panel with the engine running and pull out the relay closest to the brake booster, afr goes back up to 13.7 and rpm's back up to around 950.

Plug it back in, rpm's sink to 500 and afr back down to 10.2???

Swapped relays around and same issue.

I did a search and I am stumped

[mark houghton]

Don't forget that your rear pump relay (the closest to the brake booster) also controls the voltage to the WUR. If the WUR doesn't warm up or stay warmed up (via the internal heating coil) your AFR's will go rich (low) on you. Anyway, when you shut your car off when fully warmed up, your heating coil in the WUR will cool down and upon restarting you can expect to see a richer mix for a minute or so until the power to the WUR heats it back up. Just tuck that knowledge away for now...

One thing that caught my eye was that you turned the mixture screw "less than 1/4 turn" to richen the mix up a bit. Anything anywhere near 1/4 turn is just way way too much. Usually just a scant couple of degrees turn is all that's needed to make substantial changes in idle AFR's. I suspect that you've got her dialed in pig rich right now and would suggest that you plug in both pump relays as normal, get the car nice and warmed up, then turn that mixture screw back out until you get into the 13's for AFR.

You also mentioned replacing "all the fuses" with new ones. Dude, there is only one fuse that supplies both fuel pump relays. What are all these fuses you're referring to? Nice to have all new fuses, though.

Final comment: Make sure your new AFR guage is properly calibrated, so you're not chasing your tail on erroneous information.

[fredmeister]

Hi Mark,
Do you know if the engine heat is enough to keep the WUR in warm up condition or do you always need to have current heating the internal coil?

I thought that I read somewhere that engine heat takes over predominantly once the car is at operating temps, but your post indicated otherwise, I just wanted your clarification on this.

thanks,
fred

[mark houghton]

Originally Posted by fredmeister

Hi Mark,
Do you know if the engine heat is enough to keep the WUR in warm up condition or do you always need to have current heating the internal coil?

I thought that I read somewhere that engine heat takes over predominantly once the car is at operating temps, but your post indicated otherwise, I just wanted your clarification on this.

thanks,
fred

It's been my understanding (that I picked up from God knows where) that engine heat alone isn't quite enough to fully bring the control pressures up to warm settings...but to be honest, I've never tested it on my car by purposely unplugging the WUR when warm. I do see AFR's drop a little when re-starting an already warmed up car, so that suggests that heat soak isn't enough to keep the CP's where they belong. Should try it sometime to see what it does to the AFR's, but then the silly AAR opens up as well and could influence the test results.

Hey, I could be all wet. Anyone else want to chime in? Still learning here, don't want to spread false wisdom if I can help it.

[1986911]

Thanks for the tips Mark, I went out for a drive and started making my adjustments. Slowly everything was going back into line. I thought I was home free. Then as I am driving at a steady cruise 2800rpm in 4th, the car starts to jerk and my afm shoots to 19.5. I was rich a second before at 13.8. I let off the gas, and got an extra loud dose of decel burble. Then about 20 seconds later, everything goes back to normal, behavior and afr's. It did this intermittently (about 10 times) for the next 15 minutes until I finally got it home. I did hit the gas under this lean condition to see if it was starving for fuel. It looks like it may be a fuel pump going out as it would buck and not accelerate. I limped her home at 2k rpm in second.

What do you guys advise?

Thanks!

[oilonly]

Before buying a pump if it were me I would first ground the wire that goes to the overboost switch. JMHO

[mark houghton]

You can throw money at it and replace pieces until it stops givng you trouble. Does sound like you've got control pressures moving willy-nilly all over the place for some reason. Might be sporadic fuel pump issues, might be your WUR is acting up, might be your fuel filter is plugged.

Re-reading your original post, you mentioned that awhile ago your fuel pump(s) fuse blew...and shortly after these symptoms showed up. That's telling you something. One of your pumps might be drawing way too much current because it's beginning to fail, or maybe just dirty connections. How do they sound - the pumps - and are the relays getting like really hot? Might point you to the problem.

[1986911]

+1 on checking all other options before replacing pump.

Yep both relay's were warm when the initial issues started. My BL Wur has probably less than 1000 miles on it. It was then tuned on a dyno. I have noticed off and on a small stumble on the top end under hard acceleration. I actually thought it may be the clutch slipping but it seemed more like the car hesitating. Very, very slight.

I just looked at both pumps, the rear looks recent ( have to check records) and the front looks to be original. Has cosmeline over-spray on it still. Car has 72k on it

I take the FP relay closest to the front of the car out while its idling. Car stays the same, no change in idle sound, speed or AFR. Its like its not even there. Car is very lean on idle AFM. I hear it click off upon removing it.

I put it back in and remove rear relay and car dies. Both relays are brand new as well. I even swapped them with other just in case one was defective. I put them in when I blew the initial fuse. I changed all the fuses out as the FP fuse disintegrated in my hand when I checked it. Call it cheap piece of mind.

Looking to test front pump, any tips? Can something cause one pump to run and not the other?