Long crank time/misfire

YAMA42

MEMBER
1990 FORD F-150
4.9L
6 CYL
2WD
MANUAL
182,000 MILES

It will start but the engine has a long crank time. Once I start it, I get what feels like a multiple misfire and a loss of power going down the road. The misfire started after I found the spark plug on number four coming completely out of the manifold while still connected to the wire. I have been told it is fuel, but I have got a new fuel filter and I had the injectors cleaned. The pump usually works or it does not. This is all after replacing the plugs, plug wires, cap and rotor. Any ideas as to what's wrong?

7 Replies

HMAC300

MECHANIC
48,601 POSTS

Scan for codes and check fuel pressur with a gauge auto parts rent it. also check for a vacuum leak. here is article.
https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

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Wednesday, October 5th, 2016 AT 6:55 AM

RENEE L

ADMIN
1,257 POSTS

Hi YAMA42,

If you decide you would like to conduct the scan yourself here is a link to an article that features written step by step instructions and pictures explaining how to do the scan yourself, also I have included a link to our YouTube channel with a how to video on code scanning.

This is applicable even if your check engine light is not on.

Most scanners are inexpensive to purchase, you can purchase one online from sites like Amazon.com

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

https://youtu.be/YV3TRZwer8k

Once you have the codes please get back to us so that we can further assist you. We are always happy to help.

Thank you for visiting 2CarPros.com.

Kindest regards,

Renee
Admin

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Wednesday, October 5th, 2016 AT 3:07 PM

YAMA42

MEMBER
3 POSTS

Found a couple cracked vacuum lines, replaced them and it helped, but was not a cure. Fuel pressure checked out fine. There is still a misfire and long start, but I have got some power back. Might have to go to a shop for diagnostics.

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Wednesday, October 5th, 2016 AT 5:27 PM

KEN L

MASTER CERTIFIED MECHANIC
42,973 POSTS

I have heard of those trucks having a problem with the switching valve if you have more than one tank, I think it sucks air into the injection system. The valve is located under the bed on the drivers side I believe.

Please let us know what you find so it will help others.

Best, Ken

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Monday, October 10th, 2016 AT 5:16 PM

YAMA42

MEMBER
3 POSTS

It does have dual tanks. That could explain it sounding like it is starving for fuel, know a way of testing it? I do not want to have to keep throwing parts at it if I do not have to.