I'm pretty sure your system is the returnless type, like on my 4.0L, which would put the FP regulator in the tank, as I mentioned. It follows that the silver cylindrical thing you are talking about would have to the the fuel damper, which helps keep the pressure at an even keel while the fuel system is operating.

 

Yes Rockledge - after looking at it a bit - I know that you are correct - It is the fuel damper -

Do you know where the vacuum lign is located to that regulator? I would like to check the vacuum to it before I dropped the tank? -

By the way with the key on ignition off pressure rises to about 50 pounds - When i turn the truck on it rises to 56 and never changes with vacuum.
Thanks for your help
cscottyr

 

There is no vacuum hose like that on the mechanical returnless systems. The FP regulator in the tank does not work like a conventional regulator mounted on the fuel rail using manifold vacuum. That is why the specs for the fuel pressure on your '98 (as well as '99 and '00 models) are higher, at 64 psi +/- 8 psi, because they use the mechanical returnless system. The pressure needs to stay higher in order to maintain a minimum constant pressure against which the fuel injectors can be timed properly. Also explains why your pressure is not changing no matter what the load condition.

Overall, your (FP) seems a bit low, barely acceptable. However, add a clogged fuel filter or injectors to that equation, and problems can arise.

 

Thanks Rockledge - I will change the fuel filter and get the injectors cleaned! - maybe I will get lucky!

cscottyr

 

Hey - just one other question - do you think either the fuel filter or dirty injectors would cause a very sporatic problam like this?
cscottyr

 

Hey rockledge,

one other question - There is a device between the fuel filter and the filter damper - located on the bedrail about 2 feet closer to the engine Is this the flex fuel sensor- could it be a problem?

cscottyr

 

That's the area where an FFV sensor would be, yes. You must have a 'V" in the 8th digit position of your VIN, then? If that is the case, then your fuel pressure specs are actually very good (55 ps1 +/- 8 psi). I'd still change the filter, no matter what.

I've never really heard about a bad FFV sensor being associated with a lean contition, although I suppose it is possible, if the PCM is being given bad advice as to how much ethanol (%) is in the gas you are using, for example. Normally, though, a bad FFV sensor throws its own code.

 

Hey Rockledge,

Well I just changed out the fuel filter - Unfortunately there has been no change. Pressure is still at 56 pounds - and vacuum is still hovering at 18". I will have the fuel injectors cleaned sometime soon. Any other ideas?

scottyr

 

Well,

I think I'm going to change directions slightly. A friend who is a mechanic just stopped by and told me a story about a cam timing problem he recently encountered that is similar to what I am experiencing. I think I will take out the cam sensor and clean and inspect and maybe replace it!
cscottyr

 

Sounds like an idea. Be sure to check the entire Camshaft Position Sensor/Synchronizer Assembly while you are at it.

 

For your info - I posted the following message on the fuel injector forum also.

*Truck facts*
- Vacuum - 18" at idle - Seems to change approprietly with the throttle
- Fuel pressure - 50 pounds on start - 56 when I light the engine off. Loses pressure very very slowly when I shut the engine back off. It drops 5 pounds in the first 1/2 hour then more slowly after. This seems ok for a 3.0L with an internal fuel pump.
- After I disconnected the battery the last time - I have driven the truck a lot. The computer has not chosen a good algorithm. The truck sputters for a while on startup. It has very poor power - It is mostly undriveable at the moment. After it warms up and I park it back in the driveway -the idle is normally very bad - when this happens the vacumm is around 8 or 10". If I rev the engine a couple of times it seems to fix itself and goes back to normal.
- When the truck is sitting at idle it does not sound bad - however there is a faint occuring miss.
- When you rev the throttle - the responce is not bad -but it stumbels a little at the low end
- This truck seems to be getting worse.
- First question - If the injectors were dirty would they be likely to seal this well?
- Second question - Would the injectors cause an intermittent failure like I am experiencing?
- I physically checked the camshaft sensor today. It was clean and looked ok.

Any Ideas???
cscottyr

 

I also changed out the fuel pump today!

 

Darn, this is a tough one!

I'm not sure what else you can check. One thing maybe, I was reading through that article again I thought about the possibility of there being some kind of blockage or restriction in your exaust system? Is it the original stock exhaust?

 

I ruled out the exhaust because of the steady vacuum - though maybe I was too hasty. Actually I was reading a post you wrote in the 3.0L forum. You said that a dpfe - if it was indicating a wide open egr when it was actually closed could cause a lean problem. I haven't really checked the dpfe out- I know the egr is ok - but - I've never actually seen the valve open in any of my troubleshooting so far. Maybe I should do a little diagnostics on that ckt. What do you think? How quickly does the pcm look at the dpfe on start? - If worse comes to worse I can clean the injectors and change out the cam sensor (the assembly seemed fine). Thanks again Rockledge for all your help!
cscottyr

 

Speaking of the EGR sytem (worth investigating, IMO), this is from the 3.0L Tech Info Sticky:

Ford DPFE/EGR System Summary

Troubleshooting the Ford DPFE/EGR System (PDF)

DPFE Vacuum & Voltage Test