guy pulls into barnyard in a 90 1st gen, 200k. my brother told him i might could help him. his pump was leaking fuel out of pump head seal. ran great, just leaked. a "mechanic" replaced gasket or o-ring(not sure what seals it,never had head off a pump). it no longer leaks, but truck runs rough.misses from idle all the way to full throttle,but keeps running. it will puff black smoke when hitting throttle. my first thought was air leak or timing,firing issue.it has a knew lift pump and filter. he thinks he needs a new pump, i dont think so. the guy who fixed it cant figure it out and gave up on it i guess. i noticed the pump wasnt removed from motor to fix head leak. any ideas? i didnt have time to do much but he,s bringing truck back in a few days. thanks.

 

I don't know how you could replace the pump head o-ring without removing the pump and getting all the rollers back into the roller ring.

I would guess something fell out of place when he replaced that o-ring. Should have just pulled the pump and done a complete reseal.

 

i would think if it was in the ip it would be very noisy

 

Can you narrow the miss down to one cylinder or is it just ragged?

Just for giggles, follow the firing order around the pump. 153624 If they aren't in order make it so.

 

I have replaced the pump head seal on my VW TDI by removing the injector lines, removing the bolts and replacing 2 bolts across from each other diagonally with longer bolts. Then pick the old seal out, stretch the new seal OVER the head (scary, but no sweat) then guide the seal back into the groove. First time I did it I piched the seal and it ran EXACTLY like you describe, sucking air. I had a moment of genius when I ordered the parts and bought 2 seals. 2nd time around went perfect, still running today.
Here is a link to the instructions for non-believers

 

great info, thanks. i,ll look at the truck closer next week.