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Old gas

Purchased a 1988 F150 with I6 engine. Truck ran when parked approx. one year ago. Siphoned out the old gas, added new gas with injector cleaner, removed core from Schrader valve, cycled ignition until I had clean gas coming out of Schrader valve and then put core back in. Truck won't start.

Question is, Is there a better way (hopefully easy) to get the remaining old gas out of the injector rail and will trying to start this truck cycle the gas in the injector rail to the tank by the return line?


Staff member
How does it act when you try to start it? Unless the fuel is bad to the point of being varnish the little bit left in the injection system shouldn't be enough trouble to keep it from starting. Have you verified that you have spark?


Hitech hillbilly
Staff member
Normally a shot of starting fluid or a squirt of gas in the air Intake will start it running. Once they fire up it should push the old gas thru.
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Old Gas

Ran for a couple of seconds so I believe there is spark. Easy enough to check though. I will try a shot of starter fluid and see if it fires enough to push the old gas through. I will repost success or failure.


don't play well w others
Do you hear the fuel pump(s) cycle when you turn on the key
Listen close, they only come on for 1 second
i have had a few injected car sit for a long enough to varnish the injectors. sometimes it take a while of running on starting fluid and and some rpm to get them to clean out. intake back fires can happen to as the fuel starts to piddle out the tips
Did get it to run on starting fluid. Sufficient spark I believe. Will let it set a day and see if the clean treated fuel improves the situation in the injectors. Did hear the HP fuel pump. I was able to bleed old gas out from Schrader valve by cycling the fuel pump. Will run on starting fluid a few more times tomorrow and then think about the pressure regulator. Hope the clean treated fuel will clean it as well. Thanks for the input.


Charter Member
At this point, if it were me I'd check fuel pressure and due to vehicle age + a steel gas tank + the US gov't that requires between 0 and 10% alcohol in the fuel (an unknown at the time of sale to a consumer amount of alcohol and they don't have to tell you exactly what you are paying for, but, alcohol absorbs water in the air, then corrosion, so....) throwing a new fuel filter at it might not be a bad idea. Might be nice to check volume at the same time fuel filter replacement is being considered.


Hitech hillbilly
Staff member
I can't remember for sure, but that year might have two fuel pumps. A low pressure pump in the tank and a high pressure pump on the frame well.
Check your fuel pressure it should be around 35 at idle and 40 running if I remember correctly.


Tonto Papadapolous
Yes, it has two fuel pumps, or three fuel pumps if you have two tanks. A low pressure pump in the tank, and a high pressure on the frame rail.


don't play well w others
Usually the problem with the 2 pump system failures is the fuel tank reserve switching valve
The purpose is to keep the fuel from the tank it's being pumped from to return into the other tank
They corrode, and refuse to allow fuel to pressurize either way
You will get a small amout of pressure on the rail, but not enough to run the truck

The unit is the can in the frame rail, that has the 4 fuel lines going in, 2 coming out

I have replaced 3 of them on my 89 with 500,000 miles on it
the modern gas with alcohol eats them up
I appreciate all the input.
As per suggestions, I started it on starting fluid, ran a few seconds. Let it sit about a hour. Kept doing this over two days. Now the truck starts fine, still an injector or two not clear yet, but I've ran it to warm up temp several times and it keeps getting a little better. Now I'll let it sit for a week and let the injector cleaner do it's job and I'll start it again this coming weekend. Again, thanks for all the input.


Hitech hillbilly
Staff member
Get some seafoam or chemtool and put in in the gas it will help clean out the injectors. The chemtool is cheaper and works as good as seafoam if not better for cleaning the injectors.