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Automotive/1986 Ford 250 302 engine, one tank, 4x2, manual

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Expert: - 6/27/2008


Question
I've this truck that I mainly use to pull horse in horse 2 horse trailer. As I'm
going down highway, generally after about 30-60 minutes driving, the engine
will start cutting out like it's not getting gas, and will then quit completely.
Sometimes if I put the clutch in, it will run a while longer. Then I leave it sit
for about 15-20 minutes, and it will run again for about 20-30 minutes. Then
quit again, and I sit a while and away I go again. Except lately it's only
running 20 minutes at the beginning and is slowly getting worse, especially
when I slow for intersections or stop signs. Kind of like it's vapor locking?

It has 2 fuel pumps, one in tank and one in-line. I've had fuel filter and fuel
pump in line changed for new ones, and have checked catalytic converter
which is okay. I continue to have the same problems, and have a couple good
mechanics check it out and they cannot figure it out as it does not cut out
when I take it in or when they drive around town. Different fuels seem to
make no difference (ie ethanol vs. high octane).  I bought this truck a year
ago with 45,000 actual miles on it, and have put 12,000 miles on it. Any
ideas on what to do or check next?  Thought about changing fuel pump in
tank but hate to keep spending money when I don't know what is wrong.

thank you very much for any help or suggestions.

Answer
I fully agree that your best and most practical approach is to isolate and identify the problem rather than just throw money at it via random parts replacements in the hope that the trouble will go away.

There are a few possibilities I can suggest for you to check out:

- How clean is the fuel tank?  Is it possible that the screen on the fuel pick-up is getting plugged each time by loose particles in the tank drifting to it each time the pump is drawing fuel?

- How long has it been since the fuel filter(s) have been replaced?

- Is there a pressure or flow regulator that may have been added at some point that is either miss-set or is beginning to block?

- Vapour lock is a possibility, given that the problem surfaces once the engine has warmed up.  Older Fords in my experience (a 59 Ford and 59 Edsel, a 67 Ford and my 78 E250 class-B motorhome conversion) often suffered vapour lock in hot-weather driving due to the close proximity of the fuel lines in the engine compartment to the block.  In each of these vehicles, I eliminated this problem entirely by installing new lines fabricated from off-the-shelf straight stock and bent so as to be routed well away from hot engine surfaces and in the incoming air stream.

- Finally, how is your ignition modulator?  Usually, these active electronic devices die by sudden failure as a junction fails.  However, it is not uncommon for a failing semiconductor to "hang in" for a while, becoming "temperamental" only when it warms up.  When cooled, it will work fine again ... until it is warm again.  Ultimately, the device will fail.

If the problem is this last problem, it can be verified if you have a timing light.  Stop the vehicle and connect the light while the engine is still very warm.  Then, restart the engine and watch patiently.  A defective modulator will make itself known by a cylinder 1 spark pulse which is very random and often missing.

A bad modulator can leave you stuck out on the road, so this is one of those items for which it is a wise plan to have a spare readily at hand; this has saved me inconvenience twice in twenty years with the same vehicle (the E250).  As it happens, modulators are quite cheap, less to much less than $100, depending on your accounts and discounts.  Having one ready to go is much cheaper than dealing with alternative means of getting the vehicle home and back into service!

I do hope the above helps!

Good luck and regards ... EGK

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Ernest (Ernie) Kenward

Expertise

The challenges I most enjoy are thoughtful technical questions of a trouble-shooting nature in both electrical, power electronic and mechanical systems, mainly automotive but also machine control and small-machine PLC applications. Please note, however, that I am NOT a walking shop manual! I DO, however, make it a point to have those manuals and other service literature for those vehicles I DO own, and highly recommend that anyone serious about maintenance or modification of their vehicles do the same; MOST of your answers WILL be found there. For that matter, I do NOT go out of my way to acquire shop manuals for any vehicle I do NOT own! That being the case, any general query to me along the lines of "What is the meaning of this code read from the ECU of my 2015 XYZ?" or "Where is the fuse for the windshield washer pump found?" (try your car's electrical distribution panel for a start!) will not go far. What I do offer is a pretty good collection of literature, insights and hands-on experience with 1950s to 1980's Ford products (plus a developing database of information and practice with the Mercedes diesel cars), along with an engineering perspective and the ability to design and implement custom control, electrical and mechanical subsystems for vehicles. For that reason, I am happy to make my thoughts and efforts available to those who are of like mind and/or are seriously making a point of learning about their vehicles. Use the Opportunity to Learn!

Experience

A key skill in my work and hobby pursuits both is STRATEGIC TROUBLESHOOTING. I am a senior instructor in Electrical Engineering Technology at a leading Canadian polytechnic, my areas being Electrical Power and Industrial Control, electrical and electronics design and manufacturing, and AutoCAD and related CAD/CAE software - plus equipment problem-solving and new equipment design and prototyping. Hobby-wise, I have 30-plus years of experience in auto restoration, mostly in electrical and mechanical systems. Ongoing projects include a 1959 Edsel Corsair, my 1978 Ford E250 class-B motorhome conversion, and the care and upkeep of my Mercedes 300CD. My vehicles become engineering test beds for electrical and mechanical upgrades as ideas present themselves. This includes the design and production of circuit boards to restore or enhance features for which no OEM replacement parts are obtainable, or where better specifications or reliability can be had via newer concepts. Regarding the E250 RV conversion, I designed and continue to revise a custom power distribution system, managed by a Programmable Controller (PLC); this has made most revisions as easy as uploading new firmware as I develop it. The "mini" PLC is a powerful device for custom automotive control systems. One good example (there are many) would be the Moeller "Easy Relay"; these offer a wealth of control, monitoring and variable-and-status display options for such projects. A good example project which has worked well is that one for my RV noted above, which has been on the job - revised in firmware only - for a decade now. It is a load management and charging control system to avoid the sulfation-induced early failure that often befalls deep-cycle batteries used in RV power applications. The battery installed in 2003 lasted long enough to more tnan pay for the PLC that contributed to its longer life ... and the PLC will be there for the next battery as well!

Organizations
IEEE - senior member ... past WCC Student Activities; SME - senior member ... past chair, greater Vancouver chapter chair 318; Edsel Owners' Club - have served in various capacities on chapter executive during seventies; have been Power and Driveline resource on the Edsel Owners' Club "E-team" for more than a decade.

Education/Credentials
Graduate of UBC

Awards and Honors
Certificates of appreciation from IEEE and SME for work in student and chapter activities

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