Fuel System Clean

[SailorKane]

Newbee to this forum. I have a '97 5.0 V8. We were out of the country and it sat in the garage for 6 years and the fuel pump died. We just replaced the fuel pump, put 5 gallons of new gas and a can of techron in the nearly-empty tank, and now it starts just fine. I also replaced the fuel filter. It idles just great. When I run it around the block, sometimes it accelerates just fine, other times it'll only run at idle and any push of the pedal causes it to bog down and even stall.
But I'm sure the fuel system is full of crud from old gas. My question is: is it likely that the techron will eventually clean out the system? Or do I need to take more radical steps and actually clean out the system myself? If so, how?

 

[2000StreetRod]

Varnish

I suspect that after 6 years there will be a thick residue in the bottom of the tank similar to varnish. Fuel injector cleaner or Sea Foam will slowly dissolve the residue and contaminate the good fuel. Hopefully, the fuel filter will catch any loose particles. Even so the fuel will be degraded. One forum member in similar circumstances permanently installed a fuel pressure gauge and after a few months when the pressure had dropped significantly he changed the filter. It could take years to clean the tank following this process and there's always a chance the injectors could clog. The strain on your fuel pump because of a clogged fuel filter could result in its early failure.

Removing the tank and having it professionally cleaned may be expensive and I believe the seals are supposed to be replaced afterward.

A compromise would be to drain and remove the tank yourself. Then add a gallon of solvent that dissolves old gas, slosh it around and let soak for a day, and then drain. Repeat the process until the drained solvent looks clean.

I would also clean the MAF sensor and IAC valve with MAF sensor cleaner.

 

[ranger7ltr]

Save yourself lots of trouble and breakdowns...

I bought an Explorer that sat for 2+ years...I knew the fuel pump was dead and the gas has turned into varnish...I drained the tank, cleaned it out with gas and solvent, replaced the pump, and drove off into the sunset...

I was replacing filters every 2-3 months thanks to the varnish and other crap in the tank the fresh gasoline churns up...

I tried to clean it up with Seafoam, B-12 Chemtool, and other fuel injection/fuel cleaners and all it did was to extend the period between filter changes...It STILL stumbled, had loss of power under moderate throttle, and in general ran like crap...

Since you have to drop the tank, do yourself a BIG favor and get the tank cleaned by a radiator shop...I messed around with trying to clean the tank, running lots of cleaners in the tank, bought another tank from a junkyard[that was in the same shape as my old one], killed a new pump thanks to junk from the tank flowing through the pump strainer into the pump, dropping a full tank to retrieve said dead pump for warranty replacement, and finally draining the tank into 4 5 gallon cans to take it to a radiator shop to have them clean it out to end this cycle of disaster...

This cycle only took 10 months of agony for me to solve....

 

[SailorKane]

An update. The system pressure appeared to fluxuate a lot. We put a pressure guage on the system and got 12 pounds. And it went to zero very quickly after shutting off the key. Never got very high.
So, we replaced the fuel pressure regulator. We figured: how could the system be losing pressure, but not leaking fuel? Has to be going past the fuel pressure regulator to the return line back to the tank. Tried the pressure again, and we got 35 #, and it held pressure a long time after turning off the key (the cheap pressure tester allowed a little leakage itself).

So, now it runs much better. However, after 5-6 miles of driving, it still bogged down. Similar symptoms. seems like fuel starved. However, stop engine, wait a minute and start again, and might be OK.

Might be crud in the fuel line, but I have a hard time reconciling the abrupt change from running fine to can't-go-above-idle.

Anything else to check?

 

[ranger7ltr]

Check the fuel filter yet?

When you pull the inlet side off of the filter, have a catch pan or bottle to drain the remaining fuel into and see what it looks like.. I am willing to bet the inlet side fuel draining out is looking like dirty oil or liquid mud...

And yes it does clog the filter and cause variances in fuel pressures and deliveries...

 

[SailorKane]

Further update. After replacing the Fuel Pressure Regulator and running 5-6 miles, engine bogged again. It was nearly out of fuel. We have burned through the 5 gallons we dumped into the tank. I tried disconnecting the fuel line from the inlet of the fuel filter and pumping gas through. Less than a gallon remained in the tank, and it was quite brown, so we undoubtedly kicked up lots of remaining tank crud and clogged the fuel filter.

I also cleaned the MAF, but it looked really clean, and made no difference.

At this point, there is still crud in the tank, but while there may be another systemic problem, I think it is unlikely. Just have to decide which way to go on cleaning the remainder of the tank. I thank everyone for all the advice.

Mark.

 

[Allmost 50]

6 years is a very long time for the gas to break down and cause varnish.
My neighbor was away for 30 months. He did not add stabil before leaving. His elderly mother would crank the truck (2000 F-150 v-8) about every 3-4 weeks and let idle. After 2 years it would not crank. I replaced the battery, fuel pump and old gas. It ran perfect after that. The old pump had much varnish build up on it.