need help

dragonmaster093 · #1 (**permalink**) 07-01-2009, 02:45 AM

hey guys just traded my dentside for an 86 xlt lariet super cab 4x2 got one issue going down the road it acts like youre turning off fuel pump it cuts out for split second and does this off and on from starting stops when idling it seems to surge a little its fuel injected 5.0 it also has dual tanks po said sometimes on front tank it tries to switch tanks but idk does this on either tank but more pronounced to me on front friend said map sensor but i dont wann replace it if not bad

ctubutis · #2 (**permalink**) 07-01-2009, 07:56 AM

Have you asked the computer what it thinks might be wrong?

dragonmaster093 · #3 (**permalink**) 07-01-2009, 10:39 AM

no havent seen a check engine or other such light

Diesel_Brad · #4 (**permalink**) 07-01-2009, 10:59 AM

i would check you fuel presssure and you spark

81-F-150-Explorer · #5 (**permalink**) 07-02-2009, 06:31 PM

Quote:

Originally Posted by dragonmaster093

no havent seen a check engine or other such light

That's because it doesn't have one.

You have to physically ask the computer through a diagnostic, if it's got any codes.

First year of a proper check Engine light was 1988 F-series.

Some mid-80's between 1984-1987 have an Emission light, but this doesn't do anything but to remind you to check the computer for service codes. It comes on every 60,000 miles or so, if you have a problem or not, and needs to be reset. The Emission light is really worthless and useless.

Franklin2 · #6 (**permalink**) 07-02-2009, 07:27 PM

Yes, it might throw a ignition error code, so that would tell you the problem is there. If the computer doesn't have any codes, then you can concentrate on the fuel system. Here's a site that tells you how to pull the codes using a testlight or voltmeter.

www.fordfuelinjection.com

dragonmaster093 · #7 (**permalink**) 07-04-2009, 03:41 AM

was under hood and noticed that off map sensor is a vacuum multi port but nothing else pluged in and that up on top of plenum by thottle linkage there looks to be a vacuum port but no line could this be part of my problem

81-F-150-Explorer · #8 (**permalink**) 07-04-2009, 04:53 AM

You would have to check the Emissions lable and vacuum diagram on the radiator support.

Sometimes it is normal to have a open vacuum port like that, with a filter on it. Usually on Ported vacuum switches, or solenoids. It bleeds off vacuum depending on how it's switched.

The only way to really tell if it's supposed to be that way is the vacuum diagram on the Emission lable.

A picture of the effected component may also shed light on it.