• 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
429 f 700 with EEC4
Hello all,
Got a call the other day and was requested to go to a local business to troubleshoot a misfiring ford truck.
Now I am a retired person, and have little interest in doing such things, but one of my personal friends is their mechanic and he is pretty good at what he does, needless to say I was up for a challenge, so here is the scoop.
1985 ish. F700 with a 429 efi that misfires on cylinders 2 and 8.
spark plugs for those cylinders will fuel foul and eventually coat with oil from not firing.
compression tests good on all cylinders as well as cylinder leakdown tests good on all cylinders, I have checked
valvetrain is in good shape, no rounded off cam lobes or weak or broken valve springs.
Ignition components have been changed several times with no effect base timing is at 10 degrees with the timing shunt removed and with the timing at 10 degrees the shutter wheel align up with the hall exactly at the leading edge of #1
all fuel injectors are working electronically and have a good spray pattern at fuel pressure, catalysts are not plugged because this model was a non catalyst unit.
the ignition firing order is correct (15426378 ) and have checked the injector pairings 1458 and 2376.
this engine pulses all 4 injectors at the same time for each bank of injectors and therefore one would assume that the intake valves for any of the injector bank would either have to be in overlap or its intake valve would have to be open to create an A/F charge that would be capable of supporting combustion.
Going to check this out tomorrow.
Their mechanic states that he had checked the egr valve for operation and actually blocked it off by substituting a gasket with no opening with no effect.
I just asked him this morning, what intake port (s) is the EGR paired with ?  (could be #7 or 8 and also #2 ?
Was thinking that possibly the intake is rotted out under the egr flange where we can't see it between intake and exhaust and therefore contaminating the fuel charge for #2 and #8 ?
Thinking that I am going to charge my friends employer for the amount of sleep I lost last night, lol
This vehicle has no service codes that are hard faults and is capable of storing codes, as  we errantly got a few in there while testing.
The ecm is a one of a kind and a replacement cannot be found anywhere, however they did send the one for this truck out to a business to have it rebuilt/reconditioned.
if my buddy finds nothing in the egr system, the next step for me is going to remove the rocker covers, see when #1 injector turns on and then check the valve positions with the remaining injectors in that bank, and oh yes have checked the injector pulse rate of each and every injector.
Feel free to jump in anyone ?
How about valve timing (timing chain)?

“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
The most commonly failed component we replaced on trucks of the era was the ignition module that bolted to the side of the distributor. Typically it would cause an intermittent no-start condition as it would fail to fire either the coil or the injectors.

(03-12-2020, 11:33 AM)Hemikiller Wrote: The most commonly failed component we replaced on trucks of the era was the ignition module that bolted to the side of the distributor. Typically it would cause an intermittent no-start condition as it would fail to fire either the coil or the injectors.

+1  I have changed many of those modules over the years. They are will known for going bad.  And you need a special socket to fit down into the hole that the little bolts are in that hold it on.

[Image: CB2713-C4-93-FF-4931-AD48-B147-B4-A30-FB8.jpg]

[Image: AF3020-AC-EAC6-462-A-99-AD-12-D9-EF3-D2-B73.jpg]


1971 Mach 1
408C Stroker
C4 w/3,000 stall
8.8" Rear w/3.73's
Disc brakes all way around.

https://youtu.be/SoW1fhaFPzY  Burn Out Video. 

[Image: 044.jpg]
new ignition module, (black) installed @ firewall, reman distributor that actually had a NEW hall effect switch.
Not completely ruling out cam timing, (cover has never been removed) however bad valve timing usually affects all cylinders, but if only 2 were to have their intake valves closed or exhaust valve open too long, HMMMMM.
while turning the balancer from tdc and watching when the rotor just starts to move, I would say the valve timing would not be an issue, but I won't give up on that as an idea.
I still believe something is diluting/ degrading the a/f charge trying to go to those two cylinders.
also not ruling an intake leak that is below what one can see and is sucking in oil as some of our 351 C engines have done.
Still have not heard back from my buddy Bob to see if he had tracked down any of my leads/suggestions.
will post back after I hear from him this evening.
Just got off the phone with my buddy Bob, and he states that EGR valve is working properly ( vacuum pump opening the valve will stall the engine, and showed him how to read the evp and the evp sensor reads in range.
So that would rule out a failed passage in the intake manifold.
Tomorrow we will again check compression on those cylinders compared to the others and a cylinder leakdown test.
If nothing is out of the norm we are going to see when the noid light trips for each injector bank ( this SHOULD be exactly 360 degrees apart on the harmonic balancer) and we will note the position of the valves of each cylinder when the noid light is turned on, if any intakes are CLOSED when the noid is turned on, this WOULD indicate bad valve timing.
Will also again do the slop measuring while turning the balancer thing.
My old rule of thumb used to be 6 to 8 degrees on the balancer would indicate a sloppy chain and gears.
anyone care to add to this ?
I wish there were an actual specification when each injector bank were supposed to fire, but I am thinking that is an engineering only type thing.
Don't all jump in at once fella's
Any idea of what caused it to start, when it started, anything new added or taken off, been sitting for a long time, etc?

“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
Don, seems to have started quite a while back, with exhaust manifold bolts not staying tight and at that time they also had cylinders #1 and 2 misfiring due to a head gasket leaking compression between those cylinders.
Nothing added or removed from the vehicle other than 2 way radio removed.
all emission components still intact.
So a whopping 28K miles on this F700 so it has to sit a fair amount.
when I arrived on the scene we drained the fuel and it had no smell what so ever, didn't smell like fresh gas and didn't smell like old gas either we flushed the tank and I suggested reverse flushing the fuel injectors, they made the decision to replace all injectors.
bolt down rockers with some shims added by myself to get a little less lifter preload, some .030'' shims added.
Was wondering about the exhaust being restrictive, even ran it with both pipes dropped down and no effect.
Will post more tomorrow when I return from another go round with this beast.
It sounds like you've covered the bases pretty well. The only things else I can think of is voltages. Do you have access to an oscilloscope so you can measure the voltage pulses to the injectors? I would check and clean all grounds and pull apart all connectors, and spray them with a good electronics cleaner/protector, like DeoxIT. Poor grounds and dirty connectors can do strange things with electronics.

“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
This just in.
I guess I can only trust myself.
# 8 intake valve not sealing worth a darn, thinking these cylinder heads are to blame.
took both rockers off #8 still not sealing, air escaping thru throttle body pretty bad.
I believe the intake valve is bent.
I can open the intake valve by pushing the valve stem down with my thump and index finger (and I don't have to push very hard) the valve spring is NOT broken, do not know what the installed height is just yet but that valve is not sealing.
so that intake charge is being pushed back into cylinder #3.
cylinder #2 shows similar results, just not as bad.
Customer states that these cylinder heads came from FORD motor co. but were sold thru our local store.
something just not adding up here.
I told my buddy Bob to remove the heads and have them ready for me to inspect.
Going to see if they are the correct casting number, and should be easy to tell if they were NEW or rebuilt.
Thinking wrong valve springs or wrong installed valve spring height caused the valves to float and perhaps kissed a piston and got bent.
Will be back with some answers soon.
Share Thread:  

Users browsing this thread: 1 Guest(s)