Starting Problem

[tekkatekka]

I have a 91 ranger 4.0 4x4. It has a starting problem. It used to start very quick as the starter turned over the engine. Now after sitting all night I have to turn over the starter quite a long time before the engine starts. What seems to work is if I turn it over for 3 seconds or so, stop, then turn it over again then it starts quickly on the second try. This happens overnight or whenever it has been sitting for a while. If I try to start it right after I turn it of it starts right up like it used to. When it has been a cold night in single digits it will start quickly in the morning just like it used to on the first try. Once started it acts like it always has with a higher rpm till it warms up. I am thinking it has something to do with how it gets fuel during the cold start and wondering how the system works during that time. Also wondering if the oxygen sensor is involved with cold start.
Just before the starting problem happened some things were done to the truck.
New clutch and an engine light that lead me to change the oxygen sensor and that fixed the engine light problem. Wondering if the oxygen sensor could be bad and if that could cause the starting problem? Any help would be greatly appreciated as I need to go on a road trip soon.

 

[rtg143]

I'd check the fuel pressure in the morning. The O2 sensors don't affect the running until the engine is hot.

 

[tekkatekka]

fuel pressure test

I finally borrowed a fuel pressure tester and this is what I found.
With the key on and motor not running I grounded the fuel pump at the test plug and the pump held steady at 40 psi.
When I stopped the pump the pressure dropped slowly, within 3-4 seconds to about 8psi and held there for the 30 minutes I checked.

From what I have read pressure should hold for at least 3 minutes after pump is shut off. I don't see any visible leaks and no gas drips from the vacuum line after I take it off the the pressure regulator.

When I run the engine the pressure stays at about 33 psi at idle and when I increase rpm it fluctuates up and down a little.
While it is running I removed the vacuum hose from the pressure regulator and the psi increased to 40 psi and held.

I am assuming the cold hard starting is because there is not enough pressure in the fuel lines by morning. Wondering if it could be the pressure regulator? or what?

 

[truckerdawg]

Try smelling for gas at the top of the gas tank where the fuel line connects-sometimes these connectors become loose and allow gas to seep. Also, fuel injector O-rings do get old and shrink. And fuel injectors(it wouldn't take all of them doing this) can leak down when they go bad.

 

[tekkatekka]

thanks truckerdawg. I cannot smell any gas by the gas tank and inspected gas lines from tank to engine and no leaks. What else could be causing the system to not hold pressure??

 

[Andy D]

You have a leaky injector. a spec of dirt could do it. Using a decent cleaner may work. Regane or the higher end Techron have a detergent called polyetheramide in them. You also can buy reconditioned injectors ar send yours out to be reconned,

 

[tekkatekka]

Are you sure it is a leaking injector??

You have a leaky injector. a spec of dirt could do it. Using a decent cleaner may work. Regane or the higher end Techron have a detergent called polyetheramide in them. You also can buy reconditioned injectors ar send yours out to be reconned,

The problem is the fuel pressure drops as soon as the pump is turned off as I talked about in the earlier posts. You seem confident it is a leaking injector.
Is there a way to check if there is a leaking injector?
Could it be the pressure regulator worn so that it allows fuel to constantly bleed through to the gas return line?
Could it be the check valve I have read about after the pump? or.... anything else beside the injectors.

 

[Sasquatch_Ryda]

Its leaking back through the pump. My 91 does the same thing. I just prime the system by turning the key to the run position a few times before starting it.

Sent from my SGH-I747M using Tapatalk

 

[tekkatekka]

fuel pump check valve?

Its leaking back through the pump. My 91 does the same thing. I just prime the system by turning the key to the run position a few times before starting it.

Sent from my SGH-I747M using Tapatalk

I do a lot of stop and go driving sometimes and would like the truck to start quickly so I would like to fix this problem which only started a few weeks ago.

Is there a one way check valve as part of the pump or is it separate from the pump and where is it located?

 

[Earl43P]

It is an integral part of the fuel pump.

 

[tekkatekka]

Latest update. I unscrewed the return gas line from the pressure regulator and capped off the PR out port. I jumped the fuel pump with the key on at the test block, until the pressure gauge read 40 psi. Once again it didn't hold pressure and in a few seconds it went to 8psi and holds there for about 30 minutes and then goes to zero.
Now I think it is either one or more injectors leaking or the pump not holding pressure. Any ideas of how to figure out which it is would be greatly appreciated. My idea is to put a pressure tester somewhere on the line between the tank and the fuel rail and see if that holds pressure. This would show if it is the injectors or the fuel pump. The only places I could attach the pressure gauge would be at the fuel filter or on the drivers side of the engine compartment there is a place where the fuel pump line has one of those ford line couplers. If I open that line I would be able to pressure test it.
Anyone have any ideas of how I could attach the pressure gauge to that line either there or at the fuel filter. Wondering what kind of fittings I could rig up to get this to test??

 

[Andy D]

Get a check valve and install at the pump outlet. If that works, its the pump,

 

[tekkatekka]

Get a check valve and install at the pump outlet. If that works, its the pump,

Andy, Where do you get a check valve and how do you fit it to the pump outlet??

 

[truckerdawg]

Right now you have maybe 4 choices, maybe more if something unknown has not been brought up: leaking injector, leaking pump, leaking pressure regulator, and a leak in the line unseen. Three are expensive to try and replace hunting for the answer and the other you did not find(a line leak). Best bet sometimes is to take it to your reputable garage and let them find the answer and then you can replace the defective part. My mechanic can in 30 minutes find a problem I would search days to find and charge me $20 and sometimes nothing. He is so covered up with work he doesn't mind not doing the work himself.

 

[tekkatekka]

Right now you have maybe 4 choices, maybe more if something unknown has not been brought up: leaking injector, leaking pump, leaking pressure regulator, and a leak in the line unseen. Three are expensive to try and replace hunting for the answer and the other you did not find(a line leak). Best bet sometimes is to take it to your reputable garage and let them find the answer and then you can replace the defective part. My mechanic can in 30 minutes find a problem I would search days to find and charge me $20 and sometimes nothing. He is so covered up with work he doesn't mind not doing the work himself.

As I mentioned earlier I tested the pressure regulator by removing the return gas line and capping that port on the regulator and removing vacuum line and capping that and pressure still did not hole. So I think it is not the pressure regulator. Now I just need to find a way to pressure test the fuel line from the pump to the rail and that should tell if it is the pump or the injectors. But how to hook the guage to that line is what i need help in figuring out.
I don't know a good mechanic who does not charge a fortune for diagnosing.