Fuel delivery troubleshooting for 88 2.9L?

[BillRod]

Hi All

I have the issue from a few threads ago regarding stumbling trying to maintain 75mph on the highway with partial throttle.
The check engine light never came on but to start the diagnostics I bought an OBD1 code reader(21.99 at Checker) and the KOEO, Stored Memory and KOER test all came back with No errors. Now I think I should focus on Fuel.

Question for this thread:
Where do I find Fuel delivery troubleshooting tips?
I looked through the Tech Library section and I could not find anything specific for troubleshooting the fuel pump or fuel regulator or whatever else is involved in fuel delivery.

Can anyone point me to where I need to go to find this?

Thanks in advance for any help on this.
Bill

Here's the history:
1988 Ranger 2.9L 5spdMitsubishi, 4x4, Manual Tcase and hubs, ext cab, at least 175K miles, owned about 6 months.
Last week I cut off the stupid 1foot long cherry bomb and replaced with an oem style muffler to quiet it down, and new air filter. Today I pulled the all of the spark plugs and they looked great and consistent to eachother so I put them back in without replacing any of them. Fuel filter replaced (again) yesterday.
Traced through as much of the wiring that I could get to looking for a worn spot for potential short but found nothing.
Thanks again.
Bill

 

[IMenriched]

Hi All

I have the issue from a few threads ago regarding stumbling trying to maintain 75mph on the highway with partial throttle.
The check engine light never came on but to start the diagnostics I bought an OBD1 code reader(21.99 at Checker) and the KOEO, Stored Memory and KOER test all came back with No errors. Now I think I should focus on Fuel.

Question for this thread:
Where do I find Fuel delivery troubleshooting tips?
I looked through the Tech Library section and I could not find anything specific for troubleshooting the fuel pump or fuel regulator or whatever else is involved in fuel delivery.

Can anyone point me to where I need to go to find this?

Thanks in advance for any help on this.
Bill

Here's the history:
1988 Ranger 2.9L 5spdMitsubishi, 4x4, Manual Tcase and hubs, ext cab, at least 175K miles, owned about 6 months.
Last week I cut off the stupid 1foot long cherry bomb and replaced with an oem style muffler to quiet it down, and new air filter. Today I pulled the all of the spark plugs and they looked great and consistent to eachother so I put them back in without replacing any of them. Fuel filter replaced (again) yesterday.
Traced through as much of the wiring that I could get to looking for a worn spot for potential short but found nothing.
Thanks again.
Bill

Bill
Not trying to sound harsh....but if this is the same issue...it would be best just to continue on the same thread/post as opposed to starting a new one...it helps those who are trying to help you keep it all straight.

In a nut shell this is how it works

most of the fuel delivery is based on GPM's (gallon per minute) and ability to build pressure. not much pressure is reqiured for gas.

if pumps are worn to much..then GPM start to fall off...what might be noticed first is that with a decline in GPM's is the ability to maintain pressure. In this case there are 2 pumps...1 in the tank and 1 on the frame rail. the in tank pump, is the primer and is low pressure , around 5 psi, the frame rail pump is main stay pump which builds pressure by over supplying the need hence return lines, takes fuel to some around 40 psi.

the FPR (fuel pressure regulator) is just that..take the supply and levels it to a consistant pressure... maintain the pressure...but if the pump and or pumps can't supply enough flow to build pressure.....then a new FPR isn't going to help.

the injectors are the delivery if they are clogged then it simpply doesn't get to where it needs to be or not sealing correctly to mist the fuel ...then it will over dose the that cylinder /cylinders to which it get delivered to...

the electronics tell the injectors when to deliver the the fuel in the proper timing sequence.

the most important thing is the filter...it protects this whole system.

in your situation I'd check the system pressure...should be aound 35-40psi

 

[BillRod]

DOH!!!
I thought I was doing a good thing by separating them.
The moderator can combine them if they'd like.

Thanks for the details.
I'll look through the Chiltons and see how much that covers.

Bill

 

[AllanD]

While I am generally loathe to recommend mechanic in a can,
before proceeding further....

Buy THREE of the large bottles of Chevron "Techron"
(be specific about the name there is a similar product that is different)

Keep a 2.5gallon can of gas in the back.

run your truck down to about 1/4tank of gas and pour in two of those bottles

run your truck until it studders (Out of gas) then pour in the third bottle
and the 2gallon can of gas.

If it still suffers the same symptoms afterwards then proceed with diagnosis.

if there is any "Varnish" in the fuel system this stuff will
get ALL of it out.


AD

 

[BillRod]

Is the Chevron Techron better or different that the Gumout fuel injector cleaner in the silver plastic bottle?


I just checked the Fuel pressure using a fuel pressure gauge I just bought and the instructions in the Chiltons manual.
Every test came out OK.

Engine off and pump running = 39 psi.
Turned pump off and it only dropped 1 psi and held there for the 3 minutes stated in the manual.

Vacuum removed from the regulator and plugged, Engine running 39 psi, Accelerated the throttle a bunch of times and the pressure never moved.

"Fuel Pump OK" was the next statement on the Chiltons chart.

I guess my next steps are:
1 - Pull the pump electrical connector and see if it's dirty or anything.
2 - Try the Chevron Techron that AllanD suggested.
3 - Hook up my shiny new Fuel pressure gauge and road test it on the hiway to see if it drops pressure under the same conditions that make it stumble.


Anyone have any other thoughts or ideas?

Thanks
Bill