Ford 4000 skip

[mtny]

Good day all ,seeking help . Have a 74 4000 diesel . After warming up runs rough ,
skips etc. Have owned 5 years or so . Normal maintainence , fluids ok blah , blah.
Radiator clear . Only did this last 2 times I've run it . Thanks.

 

[Bern]

Does it blow out white smoke when it's running rough? Does it only do it at higher RPM? IF the answer is yes to both questions, you likely have a sticking auto advance mechanism in the injection pump.

 

[mtny]

No white smoke but definitely at higher rpm . Is that a pump rebuild then ?

 

[Bern]

If no white smoke, then I'd suspect air in the fuel system or simply fuel system starvation causing the misfire.

Begin your troubleshooting process by removing the fuel line on the very back of the pump. Make sure that you get a nice steady continuous stream of fuel coming out. If not, change your filter. If that doesn't fix it, check the screen in your tank shutoff valve for plugging.

 

[Ultradog MN]

I've had that skipping twice on a 3 cyl.
Both times it was the rubber hose connectors on the lines going from the filter to the pump.
One was old and shoddy and maybe started leaking air the other time they were new rubber. I added another set of pinch clamps on each side of the hoses and that fixed it.
Maybe you bumped the lines?
Easy things to check and both of mine were cheap to fix.

 

[mtny]

Fuel system was my suspicion . I had replaced filter fairy recently but she has been sitting for sometime . Thanks for the help . I don't post often on here but have gotten a wealth of knowledge from everyone .

 

[Dieseltech]

A high speed miss can be worn injection transfer pump blades and liner, that will cause a pressure drop keeping the advance curve from working correctly. Pump may also have the wrong blade rotor in too, there's a service bulletin showing that several blade rotors may need to be tried to find the correct one. The blade slot must not be in line with the outlet port, or engine MAY have what sounds like a miss. Applies only to CAV DPA three cylinder pumps. Last two three cylinder pumps I had in for repair needed a rotor change, one Ford and one Perkins.

 

[derwen1959]

Could the problem be low sulphur diesel

 

[Bern]

If the issue was retarded timing he would have noticeable white smoke, which he says he does not have.

 

[Bern]

If the problem was low sulfur fuel, everyone would be dealing with it. I think you have to go out of the country to buy high sulfur fuel.

 

[jtwat]

Also check the screen in the tank for debris.

 

[Dieseltech]

Yes, but it could be retarded just enough to make the exhaust sound like a miss and not have white smoke too. Both CAV and Stanadyne use the term Irregular Exhaust Beat, IEB now for some newer engine problems. I've seen some three cylinder DPA pumps that at light, idle delivery with two outlets working on the stand, and none from the third. That's where CAV rotor phasing is important, selecting another usually will fix the problem. CAV service training even had certain pump models that needed the advance piston "shifted" with different power and spring cap plugs.
I've always wondered why most Ford DPA pumps had eight or nine degrees pump advance, which is sixteen or eighteen at the crank and lots of Perkins three and four cylinder engines use fixed phase, no advance pumps, with the same or even higher no load speed than Fords ran. And the Perkins started and ran just as well without the advance.

 

[David G]

I would suspect an injection pump issue, my 6610 did that with bad pump, it was a simms, do not know on this one.

 

[Bern]

In my experience, timing that is retarded enough to cause a misfire causes copious quantities of white smoke. The fuel is injected, but since it's timed too late, it comes out as raw fuel.

As for the difference between the Perkins and Ford pumps, it is likely the static timing that makes them seem to run about the same. I'd dare say that the Perkins pump has static timing in the 15-20 degree BTDC range, while the Ford is closer to zero.

 

[Dieseltech]

Most Perkins engines with fixed phase pumps are timed at 23 degrees BTDC, Ford I'll bet are actually 12 to 15 BTDC, and with the advance on top of that explains why they are so noisy. No diesel engine or pump I've ever worked on used TDC, beginning of injection pump timing. TDC is only used on end of injection timing pumps, or lately with most inline pumps. Inline pumps are turned a given degree after port closing is found on test stand degree wheel, then the mark is applied for TDC timing. Deere/Bosch started doing it first years ago, now most are done this way. Port closing, plus 14 degrees, at TDC is actually 28 BTDC. Only way to know the actual timing is to look on the spec sheet.

 

[Bern]

When I said "closer to zero", I didn't mean straight up TDC. I simply meant a number less than 15. The most "retarded" engine I've ever seen was set at 8.

And yes, I am aware that Deere, Cummins and others time their engines at TDC, even though the pump has a built in offset that effectively puts it in the 20ish range.