Fuel Pump Resistor Replace Or Not ?

[Wallybally]

Hi guys,

Does anybody know when to replace the fuel pump resistor on my 1991 LS400 ?

All data I can find, including the numbering on the thing itself says that it has to be 0,73 ohm, and when i measure it with my digital multimeter, the value is 1,9 - 2,0 ohm.

Seems to me that when the secondary fuel pump relay (the yellow one, just above the resistor) switches to it, the fuel pump will be slower than spec.

Should I replace it or just completely bypass it ?

Thanks.

Wally

[landar]

You do not want to bypass it. That happens automatically with the FP relay in its 'normal' position. Otherwise the pump is running full tilt all the time and that is not good.

Now, since you are getting a higher reading than spec., did you zero out (calibrate) your ohmmeter? Often, they will read higher due to lead resistance. Just put the two leads together and however much above zero that it reads, that may be your culprit. Presuming you are not reading the resistor thru all of the wiring in the car...that adds up too. BTW, the range of the resistor is 0.67 to 0.79. Finally, and take no offense, you may have one of those cheap Harbor Freight ohmmeters...not all that accurate...especially at low readings.

[Wallybally]

Thanks for your prompt response.

Allright, putting the leads together now, and it shows 2,0 ohms as well.

That's a bit of a fluke...

Actually, that's the brandname of the thing as well. 'Fluke 11 Multimeter'

It doesn't feel cheap, feels very heavy. It has a stcker on it that says 'Calibration not required'

It should be working allright then ? Lol

I'll see if I can find some other analog meter that is more precise.

Thanks.

However, the rough idle is still there. I have found some stupid things I did and with that I had created a vacuüm leak.

Some 3" hose clamps were busted, so now all of that is repaired.

Maybe someone could tell me what the exact function is of the ACV.

I suspect that that will be the last culprit in the chain ?

Thanks.

Wally

[Exhaustgases]

The meter is reading the resistance of the probe wires. On some models as soon as its turned on or to the resistance scale you touch the probes and it should auto zero set. But on some its not so.

ACV ? Idle Air Control ?

An EGR is a good susceptible source of a vacuum leak and rough idling. Evap can as well.

[Wallybally]

Hi,

Idle Air Control I did mean, yes.

I suspect that it is rotten to the core, I'd best take it out. I've already got a bolt to put in there.

just trying to get to the bottom of it.

Thanks

Wally

[Exhaustgases]

Some folks have taken them apart and cleaned them.

I would not plug that large hole with a bolt. A small plate and home made gasket would be a better option, and not introduce aluminum chips into the inlet system.

[Wallybally]

Hi,

Sorry, just to clarify, mine is a '91 LS400, with an idle up Air Control Valve on the underside of the power steering pump. Is that cleanable ?

I was just thinking to disconnect the air hoses, cap them off at the top engine end, then leave the hoses for now, jus connect them together, until I have time to put the car on the hoist and take the valve out from the bottom.

I already have got a replacement power steering pump in, for just in case, and it came with a fitting bolt in that ACV hole, so that should work ?

Thanks.

W.

[LSPaul]

The proper IAC valve isn't THAT expensive (last one I bought was >$70 from a Toyota dealer selling on eBay) and worth doing right. The easiest way to get at it to do the change is to go at it from underneath, remove the serpentine belt, then the alternator. That will give you enough space and clearance to get at the IAC, plus be able to catch the ATF that will pour out the bottom of the opening.

Paul