1986 F-150 Couple of Issues

Thread view:

Enable EMail Alerts

Start New Thread

Thread rating:

Tom - 03 Mar 2008 23:09 GMT

I have an 1986 F-150 with the 351 engine, automatic, XLT model.
For the most part the truck is in great shape and runs good.
Problem 1:
I have noticed that I seem to smell gas anytime I get near the truck. I
haven't found any leaks and do not seem to be losing any gas. There isn't
much rust on the truck as it came originally from Texas, I haven't seen any
holes in either fuel tank. I'm wondering if the vapor cannister could be bad
and allowing the fumes to just leak out into the air? Is there any way to
check this?
Problem 2:
The engine does not like to idle well while in gear. I can start it fine
when it's warm or cold outside. It idles at high speed until it gets warmed
up, but it seems that as the choke opens it wants to die until the engine is
completely warm. If I try to put it in gear, it almost always dies....again
until the engine gets warmed up. It always restarts fine also.
I've had people tell me they can see black smoke out the pipe when I first
start it. It doesn't seem to burn oil, so it sounds like extra fuel. No, I
haven't had a chance to pull any plugs and check them (NY winter, too
cold...)
Going down the road the engine runs perfectly, no problems. Could the carb.
need adjustment, or rebuild or ???
Any thoughts/comments would be appreciated. Thanks!

Signature

Tom

Reply to this Message

Dave and Trudy - 04 Mar 2008 07:07 GMT

>I have an 1986 F-150 with the 351 engine, automatic, XLT model.
> For the most part the truck is in great shape and runs good.
[quoted text clipped - 5 lines]
> be bad and allowing the fumes to just leak out into the air? Is there any
> way to check this?

I would suspect that the activated charcoal in the canister is saturated.
You can remove it and if it is really heavy turn it upside down and see if
fuel runs out. Other than that I don't know how you would test it... Sorry.

> Problem 2:
> The engine does not like to idle well while in gear. I can start it fine
[quoted text clipped - 9 lines]
> Going down the road the engine runs perfectly, no problems. Could the
> carb. need adjustment, or rebuild or ???

Sounds like the choke linkage/mechanism is sticking. Possibly the flex hose
from the manifold oven to the air intake might be leaking or disconnected.
Easy check and easy fix, that....
DaveD

> Any thoughts/comments would be appreciated. Thanks!

Reply to this Message

Tom - 04 Mar 2008 11:39 GMT

I thought of just replacing that canister. I've seen them in LMC truck. The
manuals says it is supposed to be good for the life of the truck, but what
do they consider the life? :) The truck is 22 years old, but only has 87000
miles.
I checked to see if the choke was sticking and sprayed some cleaner around
it. It seemed OK, but I didn't check that hose. I'll look at that next.
Thanks!

Signature

Tom Clark

>
>>I have an 1986 F-150 with the 351 engine, automatic, XLT model.
[quoted text clipped - 31 lines]
>
>> Any thoughts/comments would be appreciated. Thanks!

Reply to this Message

Bob La Londe - 04 Mar 2008 16:18 GMT

>I thought of just replacing that canister. I've seen them in LMC truck. The
>manuals says it is supposed to be good for the life of the truck, but what
>do they consider the life? :) The truck is 22 years old, but only has 87000
>miles.

You may have a combination of minor problems.

22 years with only 87000 miles tells me it has probably spent a fair amount
of time sitting once or twice. Could be some varnish in the carb or some
jets partially plugged.

Partially plugged or plugged idle circuit could caus it to idle poorly.
Sticking choke or improper choke operation could cause it not warm up
properly. Sticking float valve could cause a variety of problems, like a
little gas leaking over when sitting.

Also at that age rubber under the hood could be dry rotted causing vacuum
leaks. Fixing vacuum leaks might fix your running issues. The smell of gas
is probably something else though. Maybe the carb as another poster
mentioned.

First, completely go over all of your vacuum lines to make sure they are in
good shape and not leaking anywhere. Look for cracking when you flex them
near connections.

Second, consider carb rebuild.

Signature

Bob La Londe
Fishing Arizona & The Colorado River
Fishing Forums & Contests
http://www.YumaBassMan.com

Reply to this Message

Tom - 04 Mar 2008 23:37 GMT

Excellent suggestions, thank you.
I wondered the same thing. I know it had the "normal" maintenance, brakes,
exhaust, oil changes, etc. but I don't think it ever had a carb. rebuild, or
new hoses, or anything like that.
I'm really very happy with it, it runs great going down the road, almost
zero rust. It's not a daily driver, but I'd like to make it reliable enough
to be if I want. It's more of a "fun drive" vehicle for me.
It was never a work truck. A lady owned it for a few years in texas, then
the previous owner bought it. He used to put his boat in the lake in the
spring, and take it out in the fall.
He moved to New York and garaged it for the winters, drove it only some in
the summer.
Thanks again.

Signature

Tom Clark

>>I thought of just replacing that canister. I've seen them in LMC truck.
>>The manuals says it is supposed to be good for the life of the truck, but
[quoted text clipped - 22 lines]
>
> Second, consider carb rebuild.

Reply to this Message

SC Tom - 04 Mar 2008 11:05 GMT

>I have an 1986 F-150 with the 351 engine, automatic, XLT model.
> For the most part the truck is in great shape and runs good.
[quoted text clipped - 19 lines]
> carb. need adjustment, or rebuild or ???
> Any thoughts/comments would be appreciated. Thanks!

The float valve may not be seating properly- that will cause a small amount
of gas to leak into the intake and cause the puff of black smoke on
start-up. Though not cheap any more, I'm sure a carb rebuild kit can be
found. RockAuto has one listed for $104 for your truck.

Good luck,
SC Tom

Reply to this Message

Tom - 04 Mar 2008 11:40 GMT

Would the float problem allow it to run normally, but idle bad when cold?
I wasn't sure whether to consider a rebuild or just buy a new one. I've seen
the rebuild kits at Summit, or new carbs from a few places.
I don't think it's ever had a rebuild so that might be a good idea in any
case.
Thanks for the info.

Signature

Tom Clark

>
>>I have an 1986 F-150 with the 351 engine, automatic, XLT model.
[quoted text clipped - 28 lines]
> Good luck,
> SC Tom

Reply to this Message

Chuck - 10 Mar 2008 03:56 GMT

It might-- The mixture might be too rich, since the choke is closed with a
cold engine. Forcing the choke open might cause it to run better, sort of
confirming the over rich condition.
Some carbs also have vacuum operated metering valves that can get gummed up
and stick either open or closed.
This can also cause some really frustrating intermittent rich/lean symptoms.

> Would the float problem allow it to run normally, but idle bad when cold?

> Would the float problem allow it to run normally, but idle bad when cold?
> I wasn't sure whether to consider a rebuild or just buy a new one. I've seen
[quoted text clipped - 34 lines]
> > Good luck,
> > SC Tom

Reply to this Message