I just took posession of my dads '87 F150 (5.8L / 351) truck and I have some questions.

I did some searching on here, and I think it really just served to make me ask more questions. I'm sorry if these have been asked time and time again, but I could not get a clear answer.

First off, I have the known problem of switching tanks. Now I do know I have an electronic valve. It looks like this: (sorry for the bad pic)


Now, I was told by a mechanic that this was the problem, but, if you switch from the rear tank (working one) to the front, that gas is still used out of the rear. That sound like a bad switch to me. I'm going to pull the switch and test it to be sure.

Next, when I start and drive, I can smell the exhaust, it smells really rich. I can't see or hear any leaks in the exhaust system, but I'm not going to rule that out. From reading on this site, I may need to replace the oxygen sensors (to my knowledge they are the original ones). Anything else that I should check, EGR valve?

Is it normal for the alternator gauge to be routinly on the last white line (on the high side)? But if I turn on the cab vent (to any setting) the gauge will drop a notch or two.

And my last question for the day, is it normal for the oil pressure to fluctuate? It's still always within normal, but it does worry me that it moves so much.

BTW, this truck sat for almost 2 years with no significant driving. I had my BIL take it to a mechanic in MN to get it looked over and grease/lube all the necessary joints. While driving from MN to TN the hose going from the water pump to the thermostat busted. I guess if that was all that went wrong it was good. The truck has 89,300 miles on it (no, the odometer has not rolled over, yet). And here in Memphis, I get to try to have this truck pass "inspection" this week.

Thanks in advance for any help, pointer, or knowledge!

 

That '87 5.8L is a rare bird since it still has the old carb, and I've never seen that style of valve. But it looks OE, and it looks in BAD shape, so I'd start testing it. I suspect it's jammed internally, or burned out & not switching. You don't need to pull the switch - just test at that valve in the frame for battery voltage on the R wire. It should be present with the switch in one position, and absent in the other. If so, replace the valve.

BTW
I'd like to see more of that fuel line configuration; specifically, the OTHER line (the return) from the engine back to the tanks. I think there should be another valve similar to the one shown.

There's only 1 oxygen sensor, if any. And they don't often go bad - it's more likely some OTHER problem(s) causing the exhaust smell, like damaged cat(s) or contaminated fuel. With the engine idling, stuff a rag into the tailpipe & listen for hisses & puffing to pinpoint any exhaust leaks. The pinhole in the bottom rear of the muffler is supposed to be there.

Check the EGR by applying vacuum to its port with the engine idling. If idle quality drop suddenly (it may even stall) and returns to normal when vacuum is released, the EGR valve is probably OK.

The volt gauge suggests a weak battery. Many parts stores will test batt/alt/starter free in the parking lot. Call around. If it fails, the best batteries are MotorCraft, Interstate, or Sears DieHard Gold. Get the highest CCA Group 65 you can afford in one of those brands.

That truck probably still has a working oil pressure gauge, so yes: it's normal. Most modern vehicles have a fake gauge that's designed to read steady regardless of pressure changes, which is why that one seems unusual. This describes how Ford faked it out:



When you go for inspection, KEEP THE ENGINE RUNNING for at least 30 min before beginning the test. Don't shut it off while you wait in line.

 

Steve,

Thanks for the pointers. I think tonight I figured out where the gas smell was coming from. I changed all my plugs and plug wires. The plug on the passenger side, nearest the firewall was not even "finger tight". I put the socket on and removed the plug with my fingers. YIKES!!

But that's not were the gas smell was coming from, at least not all of it. While letting the engine idle I was checking over the engine and I noticed some "dripping" on the carb. I looked from the other side and I see a nice puddle of gas on top the carb, dripping from the fuel line where the filter is. GREAT!!!

That just MIGHT explain the gas smell.

I tried to get in and see if I could tighten the fitting down but nothing I had could get on the nut, too much clutter around it.

I drop the truck off at the mechanic in the morning and have them replace the filter and a couple of loose vacuum lines.

When checking the EGR valve can too much vacuum be applied?

The battery was just replaced, but I'll have it checked out anyway.

Thanks for the tip on the oil pressure.

For the gas line, I'll have to crawl under and look at the the other frame rail, if there is another valve it'll be over there as there is on the one set of gas lines on the drivers side rail.

Thanks again!!

 

No, it's designed to easily withstand full vacuum.

 

Actually, the vapor side is just a "Y" split in the line with a line going to each tank.

 

Not the vapor - the return. Does excess fuel come back from the carb to the tanks?

 

According to my Haynes repair manual, there is no gas return line, only a vapor return. It actually described my fuel switching problem to a "T" for a change. And I just confirmed that the valve is getting 12VDC when I select the front tank, but it does not move. The manual states that when the valve has no power, it is on the rear tank, this is it's default tank.

Ryan

 

Well, that answers that!

You need a valve. When you find one, post the source & price, please. Pics, too, if you can.

 

I ordered the part from here:
http://www.trademotion.com/partlocat...?siteid=215005

$77+S&H.

I called the local ford dealership and they said they could order it but it was going to be $108.00

 

Swapped out the valve yesterday. Filled up both tanks this morning, switched to the front tank. So in a day or so I'll fill up again and hopefully the front tank will need gas and the rear one will still be full.

 

no luck, still pulling from the back tank.

I'm starting to think it might be a ground issue with the frame. So much rust down there it's not getting a good connection. I'll loosin the valve and try to scrape away some of the rust.
I did notice that the back of the valve assembly had two "spikes" if you will, like they are there to make contact with the frame ground.

 

No, the valve grounds thru the black wire. The spikes are probably for alignment.

Try unhooking the rear hose from the valve & placing a patch of fuelproof plastic (trash bag?) over the nipple, then reattaching it so it can't possibly get fuel from there.

 

Steve, I don't think that will work. The way the valve works is via the solenoid. No power to the solenoid (normal position) then the rear tank is selected. With 12v to the solenoid the front tank line is used.

While I get 12vdc at the solenoid, is it possible that not enough current is getting there to activate the solenoid?

Also, any tips for "pinching" the gas lines to prevent getting soaked by gas? At the valve the lines are a rubber type material. I would assume something to just compress them enough to block the flow would be enough but I don't want to damage them.

Thanks

 

Maybe wrap them with a rag and use a pair of vise grips?

 

That's about what I was thinking of doing.

any other ideas?