Question: Knock Sensor

[Hib Halverson]

DTC55 for the model year in question is for lean air fuel ratio at WOT.

I've said before, I think the car has a fuel supply issue, so the problem, while it could be very low fuel level, is likely somewhere between the gas in the fuel tank and the injectors.

To start, look for:

Restricted fuel pump pick-up sock
Faulty fuel pump or pump bypass check ball
Faulty fuel filter
Restricted fuel pipes or hoses
Faulty fuel pressure regulator

Good luck!

 

[John Robinson]

DTC55 for the model year in question is for lean air fuel ratio at WOT.

I've said before, I think the car has a fuel supply issue, so the problem, while it could be very low fuel level, is likely somewhere between the gas in the fuel tank and the injectors.

To start, look for:

Restricted fuel pump pick-up sock
Faulty fuel pump or pump bypass check ball
Faulty fuel filter
Restricted fuel pipes or hoses
Faulty fuel pressure regulator

Good luck!

In my post #13 to this thread I mention all the things I have done with the fuel delivery. I think I have covered all your suggestions but as strange as it would seem I have just rechecked the fuel pressure. In fact I was just sitting down to post the results.

Key on then off 42#
Engine running @ idle 40#
Pressure regulator vacuum off 47#
Engine Running at 2000 RPMs or higher a steady 38# which is within the fsm speck.
Engine off and still holding 40# after 10 min.

At this point I think I can put this to bed and relax in my chair and check out the back side of my eyelids. However if I have a bad dream and it comes back I will reopen this thread because You folks have been very generous with your knowledge.

Thanks everyone for you time and expertize.

 

[boomdriver]

If I can I try not to allow my fuel tank under 1/4. However the other day I drove it to work for the first time in a month or so, and planned on getting gas on the way home. I tried a few hard accelerations with only 3 or 4 bars, and absolutely the car simply ran out of gas. Topped the tank off and no issues.

I thought there were provisions in the tank to prevent fuel starvation from cornering and accelerating. This has been an issue whenver the car is under 1/4 of a tank. Never an issue more than 1/4.

There IS a factory installed windage tray in the tank that the pump & pick-up set in.
Unfortunately, this tray is only 5" long X 3" wide X 1.5" deep. Mine is sitting on a shelf right now. I got tired of this power loss when cornering with less than 1/2 tank of fuel, so I built a "cup" that the pump, pick-up and the return sit in. This attaches to the pump and the whole assy drops in the tank. It now can run corners down to the last 1/2 gal.
The stock tray is glued in place and breaks off and floats around inside the tank eventually...

 

[roger longman]

There IS a factory installed windage tray in the tank that the pump & pick-up set in.
Unfortunately, this tray is only 5" long X 3" wide X 1.5" deep. Mine is sitting on a shelf right now. I got tired of this power loss when cornering with less than 1/2 tank of fuel, so I built a "cup" that the pump, pick-up and the return sit in. This attaches to the pump and the whole assy drops in the tank. It now can run corners down to the last 1/2 gal.
The stock tray is glued in place and breaks off and floats around inside the tank eventually...

Hi Boom,it seems that you found the perfect solution, any chance of a picture.?......Roger.

 

[boomdriver]

Hi Boom,it seems that you found the perfect solution, any chance of a picture.?......Roger.

Its easier than that....

I'll describe my hillbilly engineering....but BEFORE everybody falls over laughing....consider that it WORKS !

It'll be coming out of the tank in Sept when my back ordered fuel sender arrives. I'll try to remember to get a pic.

When the unit is out, make note of the dimensions of the tank hole. Keep that in mind...
Find a plastic bottle thats solvent proof...anything holding some VOC's or petroleum distolates is probably good 'nuff. This is so the gasoline does not break down the plastic and create a new problem.
I used some kind of Lucas bottle I think it was. Remove all labels, scrub all glue off. Cut the top off and pull the bottle up onto the pump and pick up and return tube. I wanted as much depth as possible, like the pump were sitting in a sump. Thats basically what this is.

Then, I cut a couple small holes in the side to allow some stainless safety wire to fit thru so the bottle could be secured to the pump/tubes without interfering with the float arm. last, I cut a couple small holes in the bottom of the bottle at what would be the rear of the car so that fuel could flow in/out but not get thrown out sideways. When secured, drop the whole assembly into the tank.
This allows me to corner until I am down to that last pint of fuel. And because the return is IN the sump, it never starves for fuel. It uses everything. I also cut a thin slit in the bottom so a portion of the strainer could stick out of the bottle so that did'nt get folded up and clog up.

It make take a little work to fit the thing thru the tank opening, but it'll go.
My factory tank tray is used for coins. something that it will actually hold.

 

[Hib Halverson]

With due respect to everyone's modification solutions, I would not try to modify my way out of the problem you have.

Prior to when the problem developed in your fuel system, you didn't have problems with fuel starvation in turns.

If it were my car, I'd be looking for the reasons why it sets DTC55. Most likely, even with a full tank, the car is running short of fuel when the engine is under high load.

I might add that fuel starvation in turns was more of a problem with the 80s C4s. Newer cars had different fuel systems which resisted starvation in turns which were developed through road racing.

 

[boomdriver]

With due respect to everyone's modification solutions, I would not try to modify my way out of the problem you have.

Prior to when the problem developed in your fuel system, you didn't have problems with fuel starvation in turns.

If it were my car, I'd be looking for the reasons why it sets DTC55. Most likely, even with a full tank, the car is running short of fuel when the engine is under high load.

I might add that fuel starvation in turns was more of a problem with the 80s C4s. Newer cars had different fuel systems which resisted starvation in turns which were developed through road racing.

Understood..
My fuel tank mod was meant for Roger, who has a running C4 that starves for fuel like 99% of all 80's C4s when they get low and hit corners. This mod would'nt help the car that this thread is about. Cornering is not his problem. But, anyone else with starvation problems in corners is welcome to use this and solve their fuel problem on the track or the mountain roads.

 

[John Robinson]

Back From my Nap

Taking a look at the injectors on the right bank were I m getting a lean mixture code I discovered that 3 of the four injectors had some kind of junk covering about half of the screen in the injectors. So even though the ohms were good the fuel flow on those three at wot was not sufficient to satisfy the ecm and that is why I believe the ecm set the code 55. As they say Live and Learn. I find the exchange of ideas to be very beneficial to those who receive them and am glad that some new and original fixes are being shared. At some time when I enter my second childhood I may take my car for some track days and then i will be glad to know about how to fix sloshing fuel starvation.

 

[aklim]

Send them to FIC for servicing. That is where mine go after the other car gets back together.

 

[Hib Halverson]

Taking a look at the injectors on the right bank were I m getting a lean mixture code I discovered that 3 of the four injectors had some kind of junk covering about half of the screen in the injectors. sloshing fuel starvation.

(snip)

Bingo! John. Good work on looking for clues!

If you see visiible debris in the screen at the top of an injector, then that means the fuel filter is not doing its job or (less likely) scale, corrosion or other "stuff" is breaking loose inside the fuel lines between the filter and the injectors and getting trapped in that "filter-of-last-resort" at the top of the injectors.

Two things I'd do...first, pull all eight injectors and send them to a reputable injector service shop to be ultrasonically cleaned. I use RC Engineering in California but there are other facilities which can do this. When they clean them, they have to remove the screens so new ones are put in place after the cleaning process. Also, during the cleaning process they'll be able to find any injectors which are not functioning properly.

Secondly, if it hasn't been done in the last 24,000 miles, change the fuel filter.

You're headed down the right diagnostic path. Good luck!

 

[John Robinson]

(snip)

Bingo! John. Good work on looking for clues!

If you see visiible debris in the screen at the top of an injector, then that means the fuel filter is not doing its job or (less likely) scale, corrosion or other "stuff" is breaking loose inside the fuel lines between the filter and the injectors and getting trapped in that "filter-of-last-resort" at the top of the injectors.

Two things I'd do...first, pull all eight injectors and send them to a reputable injector service shop to be ultrasonically cleaned. I use RC Engineering in California but there are other facilities which can do this. When they clean them, they have to remove the screens so new ones are put in place after the cleaning process. Also, during the cleaning process they'll be able to find any injectors which are not functioning properly.

Secondly, if it hasn't been done in the last 24,000 miles, change the fuel filter.

You're headed down the right diagnostic path. Good luck!

I replaced the in line fuel filter about 2000 miles ago so I think the dirt on the injectors was there before I changed the filter. It all makes sense now The O2 lean was being created by three cylinders that were not getting enough fuel for highway running but ohmed OK and idled OK. Through the process of elimination I was able to reduce the size of the box I was in until I found the real source of my problem. However along the way to finding these dirty injectors I discovered a whole lot of other problems with the wiring and the grounds. Some of these were gifts from the previous owner and some were just the results of old age.(the car and me):L