4BTA hard starting

[Mark Tripi]

I wanted to get away from the other thread about 6BT hard starting, did not want to hijack the thread. I am waiting for a couple of shut off valves to block the supply and return lines to my port engine to see about loosing the fuel prime. I tried a clear line out of the razor to see if it was sucking any air and had no bubbles. Starting it up today after a day between use it required 10 pumps on the prime, cranking, 10 more pumps, more cranking and it finally kicked. When it does go there is a cloud of white/grey smoke and today I noticed the strong smell of raw diesel. I still believe there is at least one bad injector allowing fuel to drain into a cylinder and emptying the supply lines. I have no other way to explain the smoke and odor. Before I get into injectors I would like your thoughts.

Topic

[Rob Schepis]

Thanks for the follow-up

[Mark Tripi]

After sitting a couple of days we went out and started the engine. Lately I had to prime the fuel system and crank it over multiple times before it would start with a big cloud of white smoke and the smell of raw diesel. After changing the #4 injector when I tried it tonight it started up after giving about 40 seconds of pre heat. It is getting colder here! No cloud of white smoke either. Engine is running much better and turbo lag is 99% gone compared to stbd engine. Apparently the injector was allowing the fuel to drain out of the system and causing those problems.

[Mark Tripi]

Got #4 injector out this evening after letting it soak for a couple of days while waiting for the puller to come. It still fought the entire way out. This is after being rebuilt by a shop in Florida, and now with 23 hours running time.

[Mark Tripi]

I have not put a gauge on yet. But since I had a spare injector I decided to throw it in, and number 4 is my suspect. After taking off the fuel lines I took off the retaining nut, and that looked very carboned up. In the past I could easily take out an injector. This time I could not budge it. I borrowed a Cummins injector (slide hammer type) puller from my local shop and tried that. Again the injector will not budge. Mind you this is after maybe 20 hours of running. I have another type of puller coming, and will give it a try asap. I believe this to be the problem, fingers crossed.

[Tony Athens]

Slow start

Mark,

Just like the other thread, I’d do one thing at a time..

‘The simplest way to figure out if “loosing prime” is the real issue, install two good ball valves on the engine–One just before the inlet connection. One at the return line connection.. Just shut them the next time you are shutting down for a day or more.. But be sure to open both before you restart.. If nothing changes, loosing prime by fuel siphoning back or out of the system. is not the issue”.

Another thing you might do if “compression/heat is the issue slow start issue . Install a 250W oil pan heater and next time to are shutting down for a few days, run it 24-7.. If it starts easier ( no messing with the priming other than maybe a few pumps) that is the issue.. Not enough heat=very slow start and lots of smoke from un-burned fuel in the manifold when it finally does.

Have we installed a 0-50-ish PSI gauge on the on-engine fuel filter to see both priming & running pressures yet? ( how well the lift pump and check valves are do their job) Do it using a 4-10Ft 1/4” ID fuel hose with a full loop or two in it to slow down pulsations of the needle -Adding some engine oil in the hose to dampen the readings also helps that..

Tony

[Dan]

Is it possible the primer pump on the injection pump be causing this issue?

[Mark Tripi]

damn auto correct. Losing fuel prime. I tried a clear line out of the RACOR and had no bubbles!

[Author]

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