1997 V8 No-start

[Matt M.]

Truck: 1997 Mountaineer, V8, 125k miles.

Problem: Truck will crank, but nothing else - no sputtering, no almost starting. Fuel pump can be heard to run for ~2sec when key is turned. No flooding smell regardless of how long it cranks.

This started several months ago as a very intermittent problem, and has now gotten to the point that I can't trust the truck to start when I need it.

Other important info: There is an intermittent check engine light. It is a soft code, it goes on and off on its own. It does not come on in any relation to the starting problem, although I don't doubt they are related. I just can't get the light to come on anywhere near a code reader.

No-start can happen when the engine is hot, just a little warm, or bone cold. Happens on hot days and cold days. Happens on flat ground and hills.

Inertial switch is not tripped. Pedal pumping doesn't help get it started.

I have been nursing this problem along by spraying ether into the intake when it won't start, which would cause it to immediatly catch and run on the next crank. This past week, that stopped working.

If the truck won't start, it needs to sit for anywhere from 2 mins to 2 hours before it will start. Truck has spark.

So I have a fuel problem. I can hear the fuel pump, so I do not suspect it or the fuel pump relay. What else can I check in the fuel system?

I am starting to think AFM or crank position sensor. Maybe the problem is not fuel getting to the engine, but that computer doesn't know that there is air coming in, or that the engine is cranking.

Any help appreciated. I need to fix this thing ASAP.

--Matt

 

[BrianB31]

Matt, do you have a fuel pressure gage handy? Since you have a '97 it has a fuel pressure regulator on the fuel rail. Check the fuel pressure when its cold. For V8's it should be between 38-45 psi. Also when is the last time you changed your fuel filter?

Lastly, have you checked for spark?

 

[Matt M.]

I have not checked the fuel pressure, but I'll see if I can get a gauge run into the cabin to keep an eye on that.

Truck was bought used, and the paperwork shows a fuel fiter bought at the dealer but no labor charge, which makes me woder if it was actually changed.

There is spark.

--Matt

 

[BrianB31]

Matt, it's very difficult and dangerous to run fuel into the cabin. Have a friend start the vehicle after you plug in a fuel pressure gage at the Schrader valve. The valve is on the passenger side of the fuel rail up at the front.

 

[Matt M.]

Sorry Brian, I wasn't clear. The gauge is digital; the only thing running into the cabin is a wire, not fuel!

Anyway, I picked that up tonight and will get it set up tomorrow.

I also got the CEL code read: O2 sensor slow to respond. So that's not the source of my problem.

Thanks for your input Brian. Still hunting for a solution...

--Matt

 

[BrianB31]

ok..whew...just making sure.

My guess is the fuel pressure regulator is bad or the fuel filter is clogged.

Since you pulled the codes it doesnt sound like a sensor associated with starting is involved. Slow 02 response..hmm..well that wouldn't do anything for starting, just keep you in open loop.

 

[Matt M.]

The only reason my suspicion jumped to a sensor rather than the fuel system is because of the success I had with spraying ether into the intake.

With 125k, a filter and pressure regulator aren't unreasonable maintenance items. Do you know of any "gotchas" with these procedures on the V8 trucks? Or are there any DIY instructions on the web?

--Matt

 

[BrianB31]

no biggies with either. I've changed my fuel filter on the older vehicles likes ours you have to have a special tool to remove the fittings from the filter. A Haynes manual is a good investment.

Another site you can ask on is www.flatratetech.com in the ford support forum.

 

[Matt M.]

Now I've got fuel pressure samples for starting conditions and no-start conditions. No difference. Both immediately go to 38psi when the key is turned. Both hold there when cranking.

--Matt

 

[Majisto]

How is that IAC valve looking? I think if it's not working very well, the engine won't start because it won't get the proper amount of air.

 

[Matt M.]

Majisto, I must have missed that reply when you made it. I will check out the IAC tomorrow.

The most frustrating thing about an intermittent problem is making sure you have tools with you at all times so you can continue your diagnosis when you get stuck away from home.

After going through two straight weeks where my Mounty would start one out of 20 times, and never when I needed it to, it suddely reverted to giving me trouble only once a week.

Last time it wouldn't start was Saturday. I once again checked the fuel pressure to make sure nothing had changed on that front (it was fine) and then I tried unplugging the TPS. Unfortunately, I did not have multimeter with me, so that was the best I could do to rule out the TPS. It still would not start.

I plugged the TPS back in, and as I pondered my other prime suspect (the MAF) I gave it one more crank and suddenly we were in business.

--Matt

 

[double_take]

Did you try just for the hell of it to replace the O2 sensor. You said you were getting a code on it. My wifes X had that same code and had trouble startign at times. Once i replaced the sensor she naver had another issue.

Although for the life of me I can't figure out why that would have caused it to not start.

 

[Billy177]

replace the crankshaft position sensor

 

[Matt M.]

Originally posted by Billy177
replace the crankshaft position sensor

I agree that the CPS is one possible culprit, but what makes you so sure? Wouldn't a faulty MAF (i.e. it showed no air flow at all) cause an identical condition?

--Matt

 

[Matt M.]

Originally posted by double_take
Did you try just for the hell of it to replace the O2 sensor.

Nope, but since it is on the list anyway, it will get done.

--Matt

 

[Billy177]

no the engine is capible of running without the maf it will just run like crap. it would still spudder anyway from the fuel that is primed into the engine

 

[Matt M.]

Quick update:

Replaced o2 sensors, because it had to be done anyway.

Confirmed that the TPS is working correctly when the truck won't start.

Removed and cleaned the MAF and IAC.

Made an acquaintance at the local dealer who took some time to discuss with me whether the more likely culprit is the MAF or the crank position sensor.

Ordered a new crank position sensor, and will be replacing the MAF as part of my upgrade strategy, so one way or another, I will have replaced the faulty part.

Thanks again everyone.

--Matt

 

[Matt M.]

One last reply for anyone who turns up this thread in a future search:

Crankshaft position sensor replaced about a month ago, and the problem has not returned.

Case closed.

--Matt