Engine/Transmission (1994 - 1998) hard start and rough idle

[EKlem]

About a month ago my truck suddenly began to take a lot of cranking(~10 seconds with some pedal) to start. I looked through the threads here and figured that I had leaking fuel lines. I looked at my truck and saw that all the fuel lines that I could see were fairly new(I bought the truck a year ago) so I didn't replace them. I did notice that my fuel filter had a manufacturing defect and leaked fuel. I replaced it and the problem seemed to go away for a few days.

Now, the majority of the time, it takes a fair amount of cranking to start. It does not seem to matter whether the engine is warm or cold or what the air temperature is(it acts the same from 0-50 degrees). When it does start, I have to stay on the throttle for a little while and it does not run well. The truck shakes a lot and I get a lot of blue smoke and sometimes a little black smoke. After driving it for a few minutes, it runs fine except sometimes at idle. Sometimes it will idle about 100rpms below normal(900rpms) and shake the truck a lot. If I rev it a little, it will idle fine after I take my foot of the throttle. So my question is, is this an air leak in the fuel system or something else? If it is an air leak, should I start by replacing fuel lines or is there something else that would cause this?

Thanks in advance for the advice. Sorry if I am slow to respond to questions but I have very limited internet access until I get back to school when I will not have time to fix this.

 

[JoshPeters]

I'd start with the fuel supply/return lines. They can look brand new, but inside they have cracks. If you've ever cut a hose lengthwise there are 2 layers, the top layer, then a cloth mesh, then the inner layer. The inner layer will crack and start allowing air into the lines.



After that I'd look at the fuel heater, there have been a few issues with those leaking air as well.



Hopefully it's one of those 2, as they are the most common.



Josh

 

[DOWG]

Also, I would replace the overflow valve. Just because. And just because you did not mention it.

 

[EKlem]

I failed to mention in my initial post that the injection pump was rebuilt 15k ago. Can an overflow valve fail that quickly?

Since it even has trouble idling often, I would guess that this is a fairly large air leak. Would you guys agree? If so, shouldn't I be able to see evidence of it?

Thanks for the replies so far. Looks like I should be putting in some marine grade fuel lines.

 

[Joe G.]

You can't see an air leak. You can see a fuel leak. The OF valve could have failed in the box. They are not very reliable. The fuel hoses can look new and still leak air. Looks mean squat as far as those hoses are concerned. The fuel heater may look ok too. If it leaks it usually leaks in the electrical connection. A quick test is to grease up the electrical plug and put it back in. See if that affects the problem. If it does then you have a leaking fuel heater. If you live where it is not very cold you can remove the fuel heater.

 

[EKlem]

I live in NH so I can't get rid of the fuel heater but I will try greasing the electrical connection. I am also going to get some marine hose and do all of them while I can. And if that doesn't do it, I will look into the overflow valve. I appreciate all of the helpful replies. I realize that this issue has been discussed many times recently.