# Ford 6640 failing to start after rebuild



## Gallos (Jun 11, 2015)

Good afternoon

Hopefully someone can assist me. I have rebuild my Ford 6640 tractor engine, new piston liner kit, new piston and rings and bearings. Had the pump and injector redone too. Have set up the timing according to the service manual with all timing gears lining up. When trying to start the tractor it will not fire and there is white smoke plus an excess amount of diesel fuel being blown out the manifold.

I have tried to alter the injector timing by advancing and retarding the gear timing a few teeth each way, to no avail. Have tried the old fashion spill timing and still same result. Have returned the gear timing back to original factory setting and again same result.

There is plenty of compression, which you can feel on the bar when you are hand cranking the engine. as well as the sound of escaping air via the valves. I am now leaning to a botched job on either the pump or the injector, suspect they are over fueling.

If there is anything that I may have missed can you please try and give me some pointers. At the end of my tether, having to strip the front end down every time. Thanks in advance and regards.


----------



## BigT (Sep 15, 2014)

Possibly insufficient compression. Have you tried a small squirt of ether? Can you tow start it?


----------



## Fedup (Feb 25, 2014)

So just exactly how does your manual describe the process of setting the timing once all the marks on the gears are lined up? Whatever your problem may be, I doubt that moving the gears "a few teeth one way or another" will solve it. If the timing is correct, and it still won't make any attempt to start, I would be wondering about the pistons. All new stuff in there right? Numbers on the pistons are a match to the old ones? You checked the deck height once the pistons were installed? You checked and matched the thickness of the old and new headgaskets? You are quite certain the pistons are correctly installed and the crater is on the correct side? If all of this is right, then it should run.


----------



## Gallos (Jun 11, 2015)

Thank you for the replies and suggestions

The manual shows the timing to be set with #1 on the compression stroke, #1 both valves closed and #4 valves rocking. Crankshaft key at 12 o clock. You the line up the intermediate gear with timing marks on crankshaft, camshaft and injector pump timing marks. The intermediate gear can only be installed in one position where all the marks line up. Thought I had installed this incorrectly but it will not line up with all the timing marks if you try and install it incorrectly.

The pistons are an after market product and the new liners were honed to suit the new pistons. Crater in the correct position as the piston is marked indicating front on the crown. Going to try and check the compression to eliminate this, it shows this should be a minimum of 375psi. Thanks for you input will report my findings.


----------



## Fedup (Feb 25, 2014)

I wouldn't be too concerned about the marks on the gears. If they all match then it's good to go. My question is where the pump is set. I'm not aware of any internal timing marks on a DPS pump, and no effective way of spill timing. The only method I know of is the external mark on the mounting flange. My 40 series book indicates this pump mark should be set at the 0 degree mark on the inner timing gear plate. If this is correct, it should run. Any experimenting with timing should be done by rotating the pump on it's mounting bolts, not by changing the gears. 
As for the internal parts, (pistons, gaskets, etc) everything you buy is aftermarket now, no matter where you buy it. That makes checking specs, dimensions, and clearances all the more important. Third world manufacturing is geared toward fast and cheap. Precision comes in third. Taking things for granted when buying engine parts is no longer acceptable. I only hope your problem here is merely a timing issue and nothing deeper.


----------



## Gallos (Jun 11, 2015)

Hi there Fedup

With your help and guidance I have finally figured out my problem. I assumed the new after market piston to be correctly supplied and to match the old pistons, this was an over sight on my part and they are in fact a 1/4'' shorter than original. The piston was no where near protrouding the top of the block as it should be. Insufficent compression. As you have indicated never take it for granted and double check everything, especially after market parts

I feel like a complete idiot for not checking before installation and not check the protrousion either, after installation. I could kick myself, wasted all my time assuming it was a timing issue.

Thank you all for your input and solving this issue. :friends:


----------

