intermitent hard start 93 ranger

[danbowyer]

I have a 93 ranger 4x4 with a 4.0. It has been hard to start a couple of times in two weeks. I will shut the truck off after driving it and try to restart a couple of min. later and it is hard to start. I crank it and it will start after a while and I can smell raw gas. I sounds to me like is something in the ign side of things. When the truck is running I have no driveability problems.

 

[MrShorty]

My first thought was actually fuel related. One failure mode of the fuel pressure regulator (FPR) is for the diaphragm to leak, allowing unmetered fuel into the intake. When you stop, this excess fuel gets into the cylinders and "floods" them, making it hard to start until the excess fuel has dissipated. Which causes a hard warm start, but cold starts can be just fine. Easy to check: start the engine and shut it off, then pull the vacuum line that goes to the FPR. If there is gas in the vacuum line, the FPR is bad.

If that isn't it, then I would suggest a few basic diagnostic tests: pull codes, test fuel pressure (especially when it's hard to start), and check the sprak plugs and wires.

 

[danbowyer]

fuel pressure test

When I pull the vacum line off of the pressure regulator I don't have any fuel leaking. The fuel pressure bleeds off as soon as you turn off the truck. If you push the schrader valve you don't get the spray of fuel. If I test the fuel pressure with engine off it goes up to 30+ psi and then bleeds off to zero. When I start the engine the psi stays a steady 29 psi and goes close to 40 when I pull the vacum line off the regulator. Where is the pressure bleeding from? Their must be a check valve in the pump. It could be an injector bleeding off or the regulator. All of thease items are too expensive to replace if I am not sure which one is the problem. The truck has 200,000 miles on it and I have removed the injectors and had them cleaned at a shop around the 100,000 mile mark.

 

[MrShorty]

If the pressure isn't leaking off through the FPR, it's most likely a a check valve in the pump that's not working right. To test further, you have to figure out how to "clamp" off various parts of the fuel system after pressuring up to see if you can isolate the area.

In doing these fuel pressure tests, was it hard to start, or did it start normally for you while you were checking?

 

[danbowyer]

Fuel Pressure

When I was doing the test it started and ran just fine. If the fpr does not leak out the vaccum line and it works properly is it usually ok? I asked a mechanic friend of mine and he did not think it was an injector. His thought was if it bleeds off that fast it would have some driveability problems. Napa wants 130$ for a fuel pump. I have not priced the dealer yet, is oem worth the extra cost.

 

[danbowyer]

Hard start

I put a can of Sea foam and it seemed to cure the leaking check valve. I have not put the pressure gauge on it but it does have pressure on the schrader valve when I push it. The truck seems to start much easier. I still have the problem of ocassional hard start. About two minutes after shuting off warm truck I go to restart and and it cranks a long time before firing. I did not smell raw gas when it did start. With 200,000 miles on original fuel pump should I change it anyway? Dan

 

[Xpl0rer]

I never recomend changing anything just because it has so many miles on it. Although it sounds like you have isolated the problem. If you are atleast 98% sure its in the pump, go for it.

 

[MrShorty]

About two minutes after shuting off warm truck I go to restart and and it cranks a long time before firing.

How consistently can you reproduce this scenario? If you can recreate the symptoms "on demand" it will be easier to diagnose. You could drive it until it's warmed up, then shut it off, wait 2 min (while hooking up test equipment such as a fuel pressure gauge and/or running KOEO EEC-IV test), then try to start it and see if you can see something that is out of spec.

If it's truly a random event, then you will have a harder time finding it, because you have to have your stuff handy and be ready to hook it up as soon as the problem shows up.

You might backprobe the ECT or IAT to see if the temperature readings are going crazy on warm starts, but, like with the fuel pressure, you have to test them when the hard start symptoms are present. One of the reasons I suggested pulling codes is to see if the computer had seen the cause of the hard start and left a DTC in CM to help track it down.