4.3lxh Gen+ running lean

Two weeks ago this engine ran excellent smooth as could be; then last week I took it out and it cranked great idled smooth and then the choke pulled off and it died. This seems to be the engines new trick. I replaced the water seperators prior to my last trip out. Since the problem started I've checked fuel pump pressure (excellent), gave the carb a thorough cleaning but not a rebuild (it needed the cleaning but wasn't excessively bad), and checked all fuel lines for evidence of clogging and holes(no sign at all). But the problem is still there. It's a twin engine craft with a single tank and the other engine is running like a dream so I don't believe that it is a fuel issue. Thanks ahead of time for your help, I certainly haven't given up yet but some fresh input would be nice.

Re: 4.3lxh Gen+ running lean

Most carbs. have a filter under the inlet fitting did you ck. that

Re: 4.3lxh Gen+ running lean

This engine uses a weber carb and though I'm not sure if it is supposed to have an inlet filter or not I did check for one there wasn't one present. It really doesn't look like it was designed to have one either instead there are screens over each bowl inlet, I cleaned both.

Re: 4.3lxh Gen+ running lean

and then the choke pulled off and it died.

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It Sounds like some Crap in the Primary side of the Carb..........<br /><br />I'd bet that a Bench Cleaning(or Rebuild) of the Carb. would probably find the issue...........

Re: 4.3lxh Gen+ running lean

You may also have a vacuum leak somewhere. As soon as the choke comes off, there is too much air because of the leak. <br />When was the last time the engine had a complete tune up, including timing and advance timing check and carb adjustment?

Re: 4.3lxh Gen+ running lean

does it just die period..?? does it just not idle..?? will it run at throttle positions past the idle.. ?? <br /><br />does the weber card have seperate idle... intermediate and main jets.. ??<br /><br />dies as soon as the choke comes off dont really say a lot does it..<br /><br />trog100

Re: 4.3lxh Gen+ running lean

The two weber/edelbrocks I took apart, both had inlet screens right above the inlet needles. One for the primary and one for the secondary. Requires dis-assembly to get to them.

Re: 4.3lxh Gen+ running lean

All right to answer a few questions: This engine underwent a complete overhaul approx. 3 months ago (bored, heads reworked, carb rebuilt, dist. cap rotor wires and plugs replaced, etc) no significant tune-up since then (150-175 hours since then). I've also considered the possibility of a vacuum leak but haven't had the opportunity to put a gauge on yet and no luck locating a leak through sound. But thanks for seconding the possibility. As I said it dies as soon as the choke comes pulls off, engine slows (as in a lean condition) as the choke begins to pull and once fully open engine just fades into the sunset. No amount of throttle will save (aside from an immediate burst of life as a result of the initial fuel stream) the engine from killing. Thanks for the tip on the screens unfortunately I've already removed and cleaned them. Thanks for all of your help so far.

Re: 4.3lxh Gen+ running lean

Two things to do.<br /><br /><br />1. Put a vacuum guage on a non ported (intake manifold) vacuum port. With the engine warm, it should pull about 18 inches, at idle, with a steady needle. Anything other than that denotes a problem. Timing, valves, etc.<br /><br />2. Do a compression check, let's make sure the base engine is healthy. The recent rebuild makes me suspicious.

Re: 4.3lxh Gen+ running lean

apart from blocked jets/stuck needles in the primary i give up on this one.. the quick and dirty hand over the carb while revving the engine trick could be tried..<br /><br />trog100

Re: 4.3lxh Gen+ running lean

Alright ya'll I feel a bit like a jackass I finally tracked down the problem. It all stems from the fact that I checked fuel pressure while the engine was being turned over and not actually run. After I traced back the fuel pump power supply I realized that the fuel pump was powered directly from the battery while being cranked and via the alternator after the engine began running. Once the engine began running the fuel pump no longer ran and apparently there was just enough fuel in the carb to keep it running while choked but once the choke began opening it starved...everytime that's what threw me for a loop. At anyrate after tracing the wires I also realized there was a low oil pressure cut out on the fuel pump and voila the problem was found (faulty oil pressure cut out switch). By the way I ordered the switch and a mercury shop manual wiring diagrams could have saved myself and all of ya'll a lot of trouble. Thanks to everybody for their input and sorry for troubling you with, what I now realize was, misleading information. Lesson learned.

Re: 4.3lxh Gen+ running lean

Thanks to everybody for their input and sorry for troubling you with, what I now realize was, misleading information. Lesson learned.

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No Problem,...............<br /><br />I'm Sure I can speak for All the Guys here,.....<br />We Just Love Happy Endings,..... And,.. When the poster comes back,+ Tells us so... Well, That's Even Better............