HAILERS

Like the man said, *here's the deal*. Driving a 87TurboII. Only mod is a downpipe and presilencer from Mazdatrix, overhauled engine, K and N. And my version of the fuel pump rewire.

Problem: Driving along, no a/c, no lights, no radio. WOT. One voltmeter connected to the fuel pump input wire, another voltmeter to the 02 sensor. At wot I see 12.85 volts steady. The 02 reads 0.85 volts.

Now I'm driving along, lights ON, a/c ON, radio ON, cigar lighter in. WOT now. I see 12.25 volts on the fuel pump and .70 on the 02 meter.

Now I don't think I need to do the fuel pump rewire, because........prior to doing the rewire I was seeing 12.02 volts at WOT with a/c off, lights off, and .8 volts on the 02 meter. And later, I was seeing 10.88volts at WOT with the a/c ON with lights ON etc, and about the same .7volts on the 02 meter.

Why is it that when I'm at WOT with nothing on I see .85v on the 02, and if I flip the lights and a/c on at that exact moment, that the 02 falls from .85volts to .7 ??????????????????????????

I have the power for the fuel pump coming from the battery positive post going to a 30 amp relay, then to the fuel pump. You can see from the above scibbling, that it improve the voltage at the fuel pump from 10.88 volts at WOT, to 12.25 volts (a/c on and lights etc.)

In case you missed the point, why do I have .70 volts at the 02 sensor???? Instead of .85 volts? The fuel pump difference is 12.25 volts when the 02 is .70 and 12.85volts at the fuel pump when I see .85 volts from the 02 sensor???

Darn science project car.

Scott 89t2

the lower voltage is probably effecting your A/F gauge too. mine drops down leaner when I step on the brake at idle (as does the voltage)

maybe try running your gauge power and ground straight to battery and see if it changes anything.

j9fd3s

iTrader: (3)

are you making one run with everything off and another with everything on back to back? o2 sensors read leaner the hotter they get, maybe its just really hot.

mike

NZConvertible

I'm not sure about your problem but here's something to think about. The O2 sensor is not powered by the ECU or the electrical system. It's a chemical reaction the generates it's own voltage. So I don't think it's a voltage drop problem. I like j9fd3s's temperature theory. O2 sensor output is dramatically affected by temperature.

HAILERS

I don't use a air fuel meter. I use a Fluke digital volt/ohm meter. The 02 sensor is not dependent on the cars electrical system.

I'm doing these test one after another. Driving without any lights or a/c on, going wideopen throttle until I hit 100/110 mph. I get .85volts on the 02 sensor thru one volt/ohm meter and 12.85 volts from the other volt/ohm meter which goes to the fuel pump input wire (Blue).

Then, after decelerating to fifty, I do it all over again, but this time as speed increases and boost tops out, I flip the lights on and the a/c to on. The 02 sensor drops to a steady .7volts and the fuel pump drops to 12.25 volts. These are not cheap junk meters.

Whats really bugging me is, now after the fuel pump rewire, and the fuel pump now showing 12.25 volts when the lights and air conditioning on at WOT, the 02 reading is not much if any different than before the rewire when the pump voltage was 10.88 volts at WOT with the a/c and lights on.

To my way of thinking, 12.25volts is plenty and the 02 reading shouldn't drop from .85v to .7volts just because I flipped the a/c and lights on. Maybe next time I'll look at the pulse width in ms and see if the injector pulse width is changing as I flip the a/c and lights on.

Do you realize how quick 100 plus mph happens when you go WOT and try to monitor two meters? A little too quick. In the mean time I'll turn the lights and a/c off if I get on the go pedal for any length of time. I was hoping someone had seen this before. I'm thinking about undoing my rewire and starting from base figures and writing them down, then redoing the rewire. I have no real faith in 02 reading by the way, at least past stoic, but they do indicate a trend at the least. Back to the TV.

HAILERS

J9FD3S......That was a bit muddled what I wrote above. To be clear.....I've done over ten runs. Several runs I flip the a/c and lights on AFTER I see the 12.85v and .85v, then the volts drop to the 12.25 and .7v. Same run. Also done it seperatly. One run in one configuration, followed by another run in the other configuration. Results are the same, as in identical.

Heck, Scotts got me thinking about cutting the 02 wire and reading directly from the 02 with no connection at all to the ECU. Maybe some *thing* in the ECU is drawing or interfering with the 02 reading. Shouldn't be doing that, but its easier than undoing the rewire and starting all over. Goofy **** car. Gonna buy a lotto ticket, win, and buy another car with a mechanic to go with it.

HAILERS

And while I'm wasting my time away watching tv, I should state that in the past I have rigged a fuel pressure gauge to my wipers and gone for a drive. That was when I had the fuel pump wired as original. The fuel pressure would rise from forty something to close to fifty when I was at WOT. Didn't bother reading the 02 reading back then. Its been a few months. Just FYI.

Scott 89t2

hmm ok your meter shouldn't change with voltage drop then . I thought you were using a gauge off car battery power.

could it have something to do with the ecu voltage droping. causing AFM, boost sensor, temp sensor etc all to change slightly?

but I don't know. .8 to .7 is a big drop. I don't think the engine would last at .7 under WOT. you should try to test again with a wide band or EGT.


PS you're a freak LOL

HAILERS

Some progress today. Cut the 02 wire and ran it direct to the volt ohm meter. Ran up and down the hwy and had the same results.

In the first post I mentioned *my version of the pump rewire*. That consisted of doing the rewire similar to http://www.1300cc.com/howto/how2/rewire.htm except I left the fuel pump relay and resistor in their original location and ran a fused 12gauge wire from the battery positive post to the new Radio Shack relay, and cut the wires similar to http://www.1300cc.com/howto/how2/rewire.htm. It resulted in 12.85 volts at the pump during boost verses the 12.02 or so before the rewire. Well I ran a 12gauge wire this morning from the battery to the Blue fuel pump switch. Theres a 30 switch inbetween so I can flip the power on and off. That gave me 13.45 volts during boost. It also gave me the same results as before. A drop of .10 volts when the a/c is turned on.

I'm convinced I have a emi problem with the 02 sensor or inside the ECU. Darn old Radio Shack guy says he has no shielded wire. Should have asked for coax cable I reckon. Gonna swap ECU's also.

Also, in the driveway, at 4500rpm, steady, I can flip the lights on and the 02 drops 0.10 volts from the steady reading. Say the 02 reads 0.72v. Turn the lights on and it flips to 0.63v. So its not a fuel pump problem. It does this whether the pump has 13.45v going to it or 9.5 volts going to it. Same 02 sensor drop of a tenth of a volt. EMI,EMI,EMI,EMI,EMI,EMI................or ecu,ecu,ecu,...

Gregsn2toys

Ive never paid much attention to readings at 100mph, but, typical O2 sensor operation isnt a steady reading. If they read that, then theres a problem, usually a lazy sensor. Now thats on a piston engine. Rotary I wouldnt think would be different, it should be switching from lean to rich, but fairly fast. One thing to note, where are you putting your ground for your fluke meter? If your grounding it to the body, and not to the O2 sensor, the added load from the accesories could effect the ground voltage. I noticed this years ago when I had too much amp on my stereo system in my car. I bumped up wire size to the amp, but that helped only so much. I finally did something few mention, upgrade your ground at the battery. What goes in must go out. Even though the O2 sensor makes it own juice, theres other things using the body as a ground, and may kinda push it aside sort of speak. I might be off on this but give it a thought.

HAILERS

Gregsntoys........Man, part of me says no way, the exaust downpipe is metal, it bolts to the engine thats metal, and the engine is grounded to the battery and chassis. I've thought about if momentarily and just a quick say *no way jose*. But now that you've mentioned it , I need to give that a go. Thanks for the tip. I really don't think I have a fuel problem. I think I have something affecting my 02 signal. Oh, by the way, I don't have the 02 connected to the ECU since this morning. That way the car is in open loop and has a steady reading, no fipping on either side of stoic. Anyway, at wot the 02 is in open loop, and when I see the .85v at wot, its a steady .85v. But drops a tenth volt when the a/c is turned on i.e. goes to .73. I can repeat this phemonemun(sp) each and every time. I just discovered this morn that boost has nada to do with it since I can repeat the drop sitting in the driveway with the throttle at 4500 and flipping the lights on and off. I'll take what you said into consideration.

Scott 89t2

what happens if you turn on everything execpt the A/C ? lights etc. still happen? maybe it's just a load thing from the A/C rather then an electrical thing.

cause the A/C doesn't use and DC does it?

(hehe that was funny )

Scott 89t2

maybe you need one of these

http://www.shakti-innovations.com/automotive.htm

Piranha

4 tenths of a second gain in a Chevy Tahoe? I'LL TAKE 3!!!!!!!!!

HAILERS

I'll pass on the Shakti. I'm afraid with that much power I'd break my driveshaft or transmission.

How does one say *oh *****? I took my right front seat out last week and while it was out, I decided to put a bolt in the front inboard mounting hole and use it as a ground for one of my meters. I put in a nice shiney clean bolt. I'v been using it as a ground for the meter. I checked the ohms and its variable but on the whole about 17ohms. Ah fudge! I've got a wire running from the battery neg post and it seems to make a difference. At least in the driveway when the throttle is above 4000. I can turn the lights on and off now and there is no ten percent change in the 02 reading on the meter as there was before. Can't drive anymore today. Been raining and theres toooooooooo many people out there using MY road. Too much risk. GREGSN2TOYS got me on the right track. Danke.

Yeah. Shakti. Probably rates right up there with the FISH carb that will get you fifty mpg but the BIG AUTOMOBILE AND OIL COMPANIES bought off the inventor? Say did you hear about the little green men that landed in a space ship out there in the desert back in the late fortys, and the gov't is keeping it a secret because.................later.

Gregsn2toys

Now that scares me, when I give advice that someone can use,lol. GMs are notorious for ground problems and you can guess what I see in the shop mostly!

Scott 89t2

hey hey hey, re-read the 1st reply in this thread

HAILERS

SCOTT 89T2....I give you a lot of credit, but, I took that to imply IF I had one of those af gauges and it was not hooked up right, that I could have a voltage drop problem. I use a digital meter and don't use battery power or battery ground. Thats why I didn't heed the post. Butttttt looking back, I can see where it shoulda got me thinking. Danke schon. I'll be more alert next time.

HAILERS

I just went out to the turbo car with a meter. I put the neg lead on the battery neg post and the positive on the body of the 02 sensor. I got .585 K ohms. Huh? I put the lead on the downpipe. About the same. I scratched the metal, gouged the metal, still the same results. I touched the acv. Got .2 ohms. I touch anything on the engine and get .2 or .3 ohms.

I think part or all of my problem is that the downpipe is not getting a good bond with the engine because of the crush gasket b/t the downpipe and manifold.

I did the same test on the n/a car. Got .5 ohms. VEry good.

And no, I don't have that ground strap that is usually found b/t the body and exaust. There will be one in the near future. As soon as the rain goes away.

I find that quite unexpected, the .585 K ohms resistance. wadda ya think??

Scott 89t2

ya I don't have that ground strap either. but it's way back on the left muffler. a ways to go to ground the o2. I hear it was to help prevent the exhuast from rusting. even with the gasket there you would think the 3 bolts would conduct too.


what you really need is a 2 wire o2 sensor. so you can ground it to the body.

j9fd3s

iTrader: (3)

that ground strap is in the radio section of the parts fische, they list it under noise suppressor and earth cord

mike