Possiable vapor lock

purplepeopleeater · Nov 22, 2017

Hey everyone. I think I either have a vapor lock situation, or sucking air into a line. It’s a 87 ranger 2.9l 5speed. Basically the truck runs great for about 30 mind in normal light traffic. After that it slowly looses
Power and won’t rev part 2500 in any gear. After another 10-15 mins it’s sputtering and then dies. I can open the gas cap and close it again, then I’m good for another 30 mins before it all happens again. Could it be something to do with the evap system? Fuel level doesn’t effect anything, nor does ac on or off, never has problems taking gas when I fill up either. Any ideas are appreciated. Thank you for any help everyone

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adsm08 · Nov 22, 2017

Replace the gas cap.

purplepeopleeater · Nov 22, 2017

I thought about that too, it’s fairly new. Like 6 months, but it’s cheap so I’ll give it a shot. Thank you

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RonD · Nov 22, 2017

Leave gas cap loose for now

Could be EVAP solenoid stuck open, applying full engine vacuum to gas tank when ever engine is running

But you should hear a loud "WHOOOSH" of air rushing into the tank when you open the gas cap, louder than "normal"

purplepeopleeater · Nov 22, 2017

I tried leaving it loose last time, but it was barely loose. But I never hear any whooosh sound when opening the cap. I’m going to loosen the cap as much as I can before it falls off. Thank you for the advise.

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mred3 · Nov 22, 2017

CAT's might be plugging?

saskbill · Nov 22, 2017

Fuel filter(s)? Not sure how that would interact with loosening your gas cap, but the 'runs for 30 minutes' til the engine starts sputtering and doesn't have full power kinda rings a bell.

On an 87, you will have a high pressure filter (forward from the high pressure pump, on the driver's frame rail just behined where the frame rail curves up behind the front wheel). Also (most likely) a low pressure canister filter, further back on the frame rail (start looking directly below your gas cap - you'll see a big tin guard wrapped around it and the tank selector valve, if you have one)

If there's junk in your tank (rust, etc), it'll plug your low pressure filter. If your high pressure filter (metal casing) isn't shiny, or you have no idea when it was changed, might be an idea to change it (or if you see rusty gas when you disconnect fuel lines)

saskbill · Nov 23, 2017

BTW, the high pressure filter is easier to change out than the low pressure (canister) filter.

The high pressure filter connections are two plastic hairpin quick connects, and a big hose clamp that holds it in place. Its a little awkward to read cause its so far forward, and unless you're a lot skinnier than me you'll need the truck raised up some and jackstanded at the front/wheelblocked at the back (or whatever makes you comfortable you aren't gonna end up wearing a truck on your sternum!). I've never been able to unhook this filter without gas running down my arm - just be prepared for this.

The low pressure filter is protected by a heavy sheetmetal guard held by 4 rusty screws/bolts (two on top of the frame, two below). The top ones are tricky to get out - you may want to just take out one top screw and bottom screws then you can swing the shield inward (towards centreline of truck) and be able to access filter without totally removing shield). The vertical cannister that holds the filter is plastic - try loosening by hand first, use a strap wrench if you need - just don't crack the housing! The filter element is a replaceable paper/metal cartridge (if there is no filter in there, you have an accumulator, not a filter, but that should be a story for an 88). The new filter should have a new O-ring - USE THE NEW ONE and take careful not to put it in exactly where the old one is when you carefully thread the cover back on. Don't screw the guard bak into place right away - inspect for leaks after starting the truck.

Good luck. If you end up suspecting the fuel filters, I'd eyeball the front one first, unless you have reason to believe you have junk/rust in the tank.

Good luck!

purplepeopleeater · Nov 23, 2017

Thank you, I’m not if sure the high pressure filter has ever been changed. And I ended up having to do away with the low pressure one after when I tried to open it up a ended up breaking off both of the nipples. Couldn’t find a replacement so, I had to leave it off. It was however pretty rusty inside. I will replace the high pressure filter though, I’m sure it needs it anyways. Thank you again for the advise

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Possiable vapor lock

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