My vehicle runs rough after sitting for a while.

[BIGRBNSN79]

I just bought a 1994 Ford Explorer and had to replace the air box. Before replacing truck would run but roughly. I figured the loose lid on the air box was causing this problem. I replaced air box started it and seemed to do fine. I drove the truck and it felt like it was chugging. Truck sat in garage for a year never started. Can someone tell me what the fuel pressure should be? Also Im going to change the fuel filter tomorrow cause im figuring it varnished up from sitting. Truck will not start now but if a shoot a little carb cleaner into the throttle body it acts like it wants to start. Im thinking its not getting fuel. Checked fuel pressure and it was 35 psi. Please help im open to suggestions also glad to be a part of of this community.

 

[BrooklynBay]

Welcome to this forum! I've renamed your thread, and moved it into the stock 91-94 section. Clean the MAF sensor.

 

[MrShorty]

Fuel pressure should be 30 psi or so at idle with the vacuum line attached to the regulator. With the vacuum line disconnected, it should stay nearer 40 psi. Pressure should not drop off in response to increasing load on the engine.

I would suggest you review the "fuel pressure testing mini-diary" in the under the hood forum.

 

[BIGRBNSN79]

Thanks for replies!

I already cleaned MAF sensor and If you turn the key on and off 4-5 times and let fuel pump purge itself it acts like it wants to start like I said earlier the truck sat for a year in the garage without being started im going to go change the fuel filter in a bit. I put fuel pressure tester on and the first time I turned the key on it was at 15 psi then I shut key off and turned it on again and it jumped up to 35. Thats what makes me think it is the fuel filter clogged (varnished) from sitting for a year!!! Any more suggestions will be greatly appreciated!!

 

[BrooklynBay]

The gasoline might be bad after sitting for a year.

 

[BIGRBNSN79]

I am stumped!!!

Okay Truck is getting fuel to fuel rail, getting fire as well and still wont start! No check engine light when you get it to run. Put a little fuel into the throttle body and it wants to run but it wont. It acts like its running out of fuel. I take the return fuel line off what I assume is the fuel pressure regulator and hit the key and there is plenty of fuel. How do I check to make sure injectors are firing properly? Whats the ohms suppose to be when tested with an ohmeter? Im completely baffled by this problem. Could it possibly be the fuel pressure regulator??

 

[BrooklynBay]

Did you check the spark plugs & cables?

 

[BIGRBNSN79]

yes i checked to see if i was getting spark and I am getting plenty of spark. I pulled return line off top of fuel pressure regulator and gobs of fuel came out when i turned key to on position is this normal? I wouldnt think there would be that much fuel to be returned but idk. It cranks over fine acts like it wants to start but seems like its starving for fuel it had 35 psi of fuel pressure when i checked it. It wasnt running it was with key in on position. It would be 15 psi when i turned it on first time then 35 next time and then 33 next time, is that my fuel pressure regulator gone bad?????

 

[MrShorty]

I pulled return line off top of fuel pressure regulator and gobs of fuel came out when i turned key to on position is this normal? I wouldnt think there would be that much fuel to be returned but idk.

on the contrary, since there is no fuel going into the engine, all the fuel should be returning to the tank. Even when the engine is running, most of the fuel going through the fuel rail should be returned to the tank. If the fuel isn't coming through the regulator until the pressure builds up, the regulator is fine.

 

[KobeJ05]

wont putting some sea foam in tank clear the lines and help clean the injectors? i had bought a 88 buick century was sitting for 2yrs when it ran low on fuel or 1/4 tank it started acting up so i pulled in the gas station gassed it back up still nothing but i put sea foam in before i gased up and still didnt wantt to start so i left it at the gas station took 2 times to start up the next morning and ran fine.

 

[BIGRBNSN79]

OKAY! I finally got the thing started. I had the fuel pressure tester on it and it was reading 26 pounds at an idle. I think this is to low so I have a fuel pump coming. Now that farmin season is in full swing I just cant find the time to fix it. I been workin 13-14 hour days 7 days a week! PRAYIN FOR A RAINY DAY SO I CAN FIX THE PROBLEM!

 

[rhauf]

Have you checked the basics, such as spark plugs? see if they are warn out or fouled? maybe a new set of plugs and some basic tune up stuff would help. also have you checked all vacuum lines for leaks and stuff?

when the engine cranks (before it fires) does it sound like it has good compress? or does it skip by some cylinders faster? have you checked for spark to see how strong the spark it?

 

[BIGRBNSN79]

It's fixed!!!

Well I replaced the fuel pump and that didnt help. Actually it ran good for a trip to work 25 miles away and wouldnt run to get me home. The dash lights were acting funny and it would run good sometimes then run bad at other times. I bought a used brain box from a local salvage yard and installed it and it runs like a top! Thanks to everyone who offered advice on what to look for!

 

[MrShorty]

Glad you got it fixed. If I may ask, how did you determine that the "brain box" was faulty? Diagnosis on something like this is often 90% of the battle, and it might help the rest of us if we knew how you determined what was bad.

 

[BrooklynBay]

Thanks for the update! I'm also curious about how you figured it out.

 

[KobeJ05]

Thanks for the update! I'm also curious about how you figured it out.

 

[BIGRBNSN79]

Well basically it was a wild guess but i noticed that the anti theft light would be flashing when the key was off and other times it would not be there at all so i knew it was something electrical. I figured a used brain box from the junkyard for 40 dollars wasnt a bad attempt at fixing it so I tried that and it worked. I appreciate all the help from you guys.