Yanmar 3GM hard starting after injector service

[Skunther]

After a long crank with batteries combined and a failed start, I check the battery cables at the starter solenoid in the engine compartment and none were hot. The starter sounds as healthy as it ever did under my ownership. Are these the cables you mean?

 

[B27]

The proper test for a lift pump is a pressure gauge...

Adding an electric pump before the lift pump may be an easier test.

 

[vas]

How did you determine your lift pump was faulty?

a tee between the lift pump and the high pressure one. a decent pressure gauge on the tee (no need for more than a couple of bar). Once you manage to get it running (no matter how really) you see that pressure will be at circa 1bar (at least that's where mine is now with the el.pump). Shut engine down. Probably will drop a bit to circa 500-600mbar. Leave it for a few hours. If it's dropped, you know you have a leak. 99% it's from the crappy lift pump. Of course could be from the crappy yanmar engine mount filter.
For the lift pump, just replace, don't bother trying to fix it!
For the filter, check screws, plastic washer on bleed screw, o-rings (2 iirc) and put it all back together. Even better throw it away and get a decent filter

V.

 

[Skunther]

a tee between the lift pump and the high pressure one. a decent pressure gauge on the tee (no need for more than a couple of bar). Once you manage to get it running (no matter how really) you see that pressure will be at circa 1bar (at least that's where mine is now with the el.pump). Shut engine down. Probably will drop a bit to circa 500-600mbar. Leave it for a few hours. If it's dropped, you know you have a leak. 99% it's from the crappy lift pump. Of course could be from the crappy yanmar engine mount filter.
For the lift pump, just replace, don't bother trying to fix it!
For the filter, check screws, plastic washer on bleed screw, o-rings (2 iirc) and put it all back together. Even better throw it away and get a decent filter

V.

I’m smacking my head - I have a pressure gauge between my primary and secondary filters. I suppose it could just as easily indicate a leak in the system? It seems negative pressure would equalize by drawing from the tank tho. Where exactly in the system does the cutoff stop cutoff the fuel supply?

 

[vas]

I’m smacking my head - I have a pressure gauge between my primary and secondary filters. I suppose it could just as easily indicate a leak in the system? It seems negative pressure would equalize by drawing from the tank tho. Where exactly in the system does the cutoff stop cutoff the fuel supply?

what does your gauge show with engine on and off? bet with engine off it shows zero.
since the only nonreturn valve in the system is the actual lift pump (effectively it incorporates a non return valve!) the pressure gauge must be AFTER the lift pump...

 

[Skunther]

Would more cranking amps make a difference in starting compression? I currently have a new battery that’s rated at 550CCA, but it’s not holding a charge and I need to return it. I’m thinking of possibly picking up a different 24DP that had 800 CCA, but it costs roughly twice as much and I don’t know if it will make any difference.

 

[Skunther]

i attached a 1000amp jump starter battery, and the engine started without ether in roughly 8 seconds. Not bad. And then, strange enough, rpm under load at WOT maxed at 3500, while it had previously maxed at 3250 (prior to the work in question was done to the engine last fall, I could get roughly 3500). I had followed the advise of some others on SBO who had recommended running the engine under load, hard at WOT, throttling back and up periodically over a period of 4 hours to see if that might seat the rings (if they are the culprit for the low compression the shop tested). I’m not sure if that had the desired effect, but it does seem a definite improvement. I plan to pick up a dual purpose battery with 1000 MCA to replace my current one (with ~675 MCA), and hope that does the trick.