TommyL

I have a code 64 "lean bank O2 right side" on my 90 ZR-1. The car is due for E-Testing but I am positive it won't pass until this issue is corrected. The car runs great until it gets hot then it spits, runs rough and looses power. I installed RC injectors, Magnecor wires, factory plugs vacuum lines ect about 10 years ago and there might be 30,000 kms (20,000 miles) on them. I am wondering if it could be the fuel pumps, ignition module, coil packs or perhaps a bad injector.. maybe even a plugged injector?

I have been reading online and it seems the answer to this code 64 is all over the place (people guessing) and suggesting anything from fuel regulator, wires, plugs, coil packs this or that module.. not really any help.

I have always received very good information from this group and any input would be greatly appreciated.

mike100

If it runs good at start-up (open loop where it does not use oxygen sensor input) and then goes crazy when it goes to closed loop, most likely the oxygen sensor is toast. Autozone sells the USA made Bosch units for $44. Barring a proper diagnosis with a scanner or an electrical meter on the sensor, it is a cheap first guess.

Dominic Sorresso

Is this happening just cruising or when you are going full throttle? Does this happen if it is sitting there at idle?

gbrtng

might be a poor connection - happened to my 91 once - wiggled it and all better.

TommyL

Happens when cruising and if I let it idle long enough it seems to run rough once it gets to operating temp. Because the engine light comes on once it reaches operating temp, I haven't run it at full throttle. The car has been parked for 5 days now until I get a chance to look at it. I am hoping it is something simple like the O2... that would be an easy fix. Thanks for the replies, you guys are always helpful and Happy Daddy's day to everyone!

Z51JEFF

Replacing the sensor is easy,getting it plugged in is a pain in the ***. I think it's the right side but can't remember. The plug is up against the block and very hard to get to.

TommyL

Jeff, I did one years ago and can't recall what side it was but yes it was a pain in the *** and I think it took me about an hour to get it plugged in and 3 mins to install the sensor into the exhaust. Hopefully this solves the issue as I don't really want to go through process of elimination replacing parts one at a time. This morning I fired it up and it does run great until it reaches temp, then runs a little rough. I'm thinking you guys might be correct in that the O2 is pooched. Once I replace it I will report back with the outcome.

bad-zr1

If you have a fuel pressure gauge put it on and start it up. See if your pressure starts dropping once the water temp. gets to 176. If it does you have a fuel pump going out as the secondary pump will shut off at 176 and you are running only on the primary (bad) pump.

glass slipper

You can "rent" a fuel pressure gage kit from AutoZone for free and do the test above...it's the easiest and cheapest test you can do. I did the same thing for a different car but taped the gage to the windshield to see it while I drove since my problem was in the upper RPM range, you could watch the fuel pressure drop as RPM increased confirming a fuel pump going bad.

Excellent suggestion bad-zr1.

RICHARD TILL

When i had the right oxygen sensor code i loosened the motor mount bolts and jacked up the engine. The right side sensor is a pain in the butt but the left, not so much. I swapped sides with the sensors and the code followed. That was my process of elimination. Ordered a new sensor and installed it on the left side. Problem solved.

Paul Workman

Just for something to tuck away, should you ever install headers, is to drill a hole and install an O2 sensor bung on the header collector so the sensor juts out (more or less) horizontally toward the outboard side of the car. This will facilitate easy installation and/or easy access to the wideband sensor when tuning WOT parameters.

As for getting damaged, I got my Z off the ground something like 3-4 feet and dropped back to soft earth...w/o shearing off the O2s (at least). Plus, I've been thu several "frog strangler" rains over the past 4 years w/o issues (knock on wood!!).

FWIW, Paul.

Dominic Sorresso

If ur replacing O2s, let me recommend the AC or Denso rather than the Bosch. More consistent and accurate.

TommyL

All good info guys! Initially, I did think it was a fuel pump and might still be. I should likely replace them anyway as they are original. Anyone have part numbers for the pumps? I know they are Suburban units but knowing my dealer they won't have a clue what I'm talking about.

Thanks again you guys are amazing.

mike100

I hear these are the new hot ticket and dirt cheap too.
https://www.rockauto.com/catalog/raf...ktemplate=true

Hib Halverson

A 20 dollar fuel pump? Yeah, "mike100" they're the "hot ticket" alright.

As for this car with sets DTC64, lean, right bank....it's possible but unlikely that code is caused by a fuel pump problem. If you had one of the pumps out or one of them is weak, it would effect both banks of cylinders not just one because both sides of the engine are fed by the pumps.

It is true that the two pumps in an ZR-1s fuel pump/pick-up assembly were used by GM on some Big-Block trucks of the late 80s and 90s but you have to make sure you get the right two pumps.

Also, while it is possible to change just the two pumps it's usually not a bolt in operation. Somewhere on the ZR-1 Net web site is a how-to article about replacing just the two pumps in a ZR-1 pump/pick-up assembly.

A couple of years ago, I wanted to do the pumps in my '95 and after looking at the amount of work involved to graft the GM BB truck pumps into the ZR-1 pump/pick-up assembly, I decided just to buy a replacement pump assembly from Zip Products.

That said...back to my point about the engine being lean on only one bank.

If you have the factory service manual and a scan testing, I'd diagnose the code with the FSM's troubleshooting info.

If you don't have the books and are reduced to guessing, I'd first try looking for a vacuum leak into the right bank. You could also try replacing the right side O2S. Use either Delphi or Denso sensors.

Lastly, you talked about running a fuel pressure test. What were the results?

Paul Workman

While there are many ways to "skin a cat", I've used the following (easy?) procedures to troubleshoot both faulty O2s and fuel delivery issues in the past. (I don't know 'bout anyone else, but I find the FSM both a blessing and a frustration when it comes to troubleshooting. So, I hope this helps...)

While a code or a scan indicating an O2 sensor fault (and because both cylinder banks are fed from both pumps), it skews the majority of suspicion toward the O2.

However, it is so simple to verify the pumps and the pressure - even under actual WOT conditions, IMO is is worth checking out the pumps first anyway - you don't even need to jack up the car to determine if you need to proceed further.

But first things first: Scanning (OBD-I, btw) will allow you to compare the left-right bank O2 performance for clues regarding the O2s. Compare the number of CROSS-COUNTS and voltage ranges. A lazy O2 will have sluggish (fewer) cross-counts, and the average (or mean) voltage range my be skewed more toward "zero" volts; an indication the O2 is dying. But, in addition, the computer will see this as a lean condition on that bank, so the BLOCK LEARN fueling value will be elevated, compared to the "normal" side.

The combo of the two just about guarantees the O2 is/has gone bad. (Note: If swapping the O2 with the one on the opposite bank results in the problem following the sensor, then you have your verification. I'd go with Marc or Pete or Dominic's recommendation, far as purchasing replacement O2s goes, because tuning is "their thing" and they would have the latest info.)

As for the pumps: One easy indicator of a pump failing is to measure the total current draw of the combination of the two pumps.

Configuring the DVM for 10A (10 ampere) operation



Then, with the ignition switch OFF, connect the POS terminal of the battery to the fuel pump test lead (short red wire jutting out of the wire loom near the windshield wiper motor) in series with the DVM to see the combined current draw for the two pumps.



Together they normally read between 8 to 10 amperes. And, by removing one of the pump fuses, one can deduce the current draw performance for each individual pump as well.

Continuing the verification process, (also) with the ignition key OFF, assuming current draw for the combination is in the normal "window" of acceptance, a fuel pressure gauge should indicate approx 53 psi ± a pound or two. And, once disconnected from the power source, the pressure should hold to within a pound or two for 15-20 minutes (I found), indicating (for one thing) your injectors are not leaking, but also the fuel pump check valves and various connections are operating properly.

Performing a dynamic fuel pressure test: The fuel filter is easy enough to replace that it can be done in a routine manner. And, if it hasn't been changed in the last year or two, it is easy enough to do - before going onto the next step, if you wish. Anyway, the dynamic pressure test can be done by extending the fuel pressure gauge so that it can be taped to the windshield and observed while driving.



While cruising, the secondary pump is not running, and fuel pressure should read about 43-46 psi. But, at WOT, the pressure should jump to around 54 psi. If the pressure is low, then either there is a bad fuel pump or perhaps the fuel filter is clogged, or some other obstruction exists. (I'd start with the fuel filter first before conducting further investigation to isolate the location of the (obstruction)).

mike100

I'm putting my money where my mouth is on this one (all $39 of it- don't forget the 5% rockauto discount code). Should be able to test these out this Saturday to see if it can maintain more than 50 psi at 7000 rpm.

mike100

UPDATE: pair of $19 fuel pumps running like champs. 51 or 52 psi all the way to redline. Hopefully they have longevity. Makes you wonder how many middlemen and private label repackaging there is in the parts business.