code 55
 

1990 368 cu. in. 4l8OE transmission.
Went for a drive all temp normal ,good fuel pressure. In 3rd gear nailed it got a code 55 ( fuel lean monitor ) slowed down went back to garage . Did fuel test
both pumps connected receive a reading of 6.45 amps. removed Fp1 checked
the reading again it showed 4.29 amps. From memory it looks like secondary
fuel pump needs to be replaced. I'am i correct?
Thanks
John

Re: code 55
 

I'm curious as well. I threw a 55 last weekend. The code cleared itself with a fresh on/off cycle and I needed to clear it from the history code.

Re: code 55
 

I would do both.

Re: code 55
 

Ordered new pumps from Rock Auto P-240KC yesterday

John

Re: code 55
 

I'll have to soon look at doing the same, however I have an option...

I have a complete NOS fuel sender with two pumps. Never out of the box. Is there a way to bench test these pumps to make sure they are still good? I suppose I can put a quick 12v to them to see if they spin, but do I need to worry about any degradation after almost 30 years?

Also, any tips on the install of a "double pumper" (reminds me of my roadrunner, Holley days)? I've done several C4 pump removes and installs, so is there any ZR1 specific tips?

Re: code 55
 

John, Thanks for the part number. I looked up Rock auto and found the P-240KC (obviously x2) and found another option a DELPHI FE0039.

The P-240KC is significantly cheaper and I've seen other rave about DELPHI. Just curious as to why you went with the P-240KC? I'm getting geared up to do this project (as PM) as my 83k '91 has a bit of hard time starting when cold and I got a lean code 55 at WOT at about 7k rpms.

Re: code 55
 

Most of the owners are using the P-240KC for replacement. I had trouble with the hose feeding the fuel rails blowing off ,because of wrong size hose clamps being used. At that time 2 years ago i did not replace the pumps as fuel showed around 52 lbs at start up then drop to 48 lbs at idle. I have an electric fuel
pressure gauge mounted on my dash along with tach and air/fuel gauge. Pryor to code 55 i saw fuel pressure drop to 42 lbs it didn't dawn on me until i made my first DYNO run check engine light came on. stopped the test and brought i home. Put TECH-1A on at home ,checked codes only code 55 showed.So did the test for amp draw it showed 6.45 amp for both pumps. New pumps will arrive Tuesday afternoon and the work goes on.

John

Re: code 55
 

John, any luck?

I swapped my fuel/pump sending unit today. Out came my 84k (still functioning) and in went a NOS sending unit and pumps. Reasonably straight forward install and I changed out the filter. I went for a quick ride and topped off the tank. The gauge reads full and so far no leaks, but I was only able to get her up to about 5.5k due to short roads.

Re: code 55
 

I received my new pumps Thursday afternoon.I changed the clamps on the primary pump to a screw type because ready for this the smooth clamp came off after 3 tries while checking the operation. So take out pump assembly and replaced the clamp on the primary pump. Retest ok I did noticed that the amp with both showed only 7.1 amp draw. Battery voltage was 12.5 volts during this test.So i do not get 8 + amps draw.The nipple on the fuel pump has no ridge on the end of the pump feed and that is why the hose came off. Fuel pressure reading was 50 lbs with key on after starting pressure dropped to 42-43 lbs.
i believe the electric fuel gauge reads a little low ,won't know until i get my mechanical gauge back. Next up driver side window motor stops working at
times. Work goes on.
John

Re: code 55
 

Ok update, car runs good after i replaced the smooth clamps with screw type.
I got my mechanical fuel pressure gauge back and it read about 2 lbs higher then electrical gauge. (mechanical read 52 lbs electric read 50 lbs).
Next is replace driver side window motor, but that will have to wait as i'am going to the $100,000 foot brake race in Tenn. this coming weekend. As a pit crew not as as a driver.
John