96 787 strange starting problem

[lilngineer]

Hi,

I recently rebuilt my carbs on my 96 challenger. I set all adjustment to factory specs.

The boat always starts right up out of the water and at first launch. However, after I've driven in for a bit at various speeds and shut of the engine to float or anchor, it consistantly is hard to start. It will only start by pushing the throttle forward. The choke doesn't help either.

Any suggestions on what may be causing this?

Also, when I first come out of the no wake zone, I noticed the engine is loading up because it wants to hesistate and throws a bit of an exhaust cloud. Low speed adjustment??

Could the two be related?


Thanks,

Jason

 

[timmyboy76]

when you "rebuilt" the carbs, did you re-use the stock n/s spring, or install a "colored" spring from the rebuild package?
ALso, you make sure the eccelerator pump anf fittings were cleaned out, and see if it were "squirting"

 

[lilngineer]

I did replace the needle seat springs with ones from the kit. I remember there were two sets, but I used the ones that appeared to match the originals.

I cleaned and blew out all of the fittings, but did not test for "squirting". How would I do that?

 

[timmyboy76]

pull the flame arrestor off, and since you've started ur boat, then the fuel system is primed, SO...move the throttle lever, and at same time, look down inside carb, you'll see gas squirt'n from the bronze fitting...
If you have the stock spring, I recommend you, put it back in...that spring you installed, is about 20-25 grams, heavier than stock...:cheers:

 

[lilngineer]

My original springs (in there when I disassembled) are like a light olive green color. Are these the correct ones?

 

[lilngineer]

Well I changed back to the olive colored springs from the golden looking ones and it seems like it starts back up after running a little easier, but it is still more difficult than when first launched or on land.

Any other ideas?

 

[lilngineer]

Well I changed back to the olive colored springs from the golden looking ones and it seems like it starts back up after running a little easier, but it is still more difficult than when first launched or on land.

Any other ideas?

 

[timmyboy76]

more specific

quote...but it is still more difficult than when first launched or on land.

What you mean? Did you make sure, the "float-arm", was level with inner carb body?

 

[lilngineer]

Float arms are level.

What I mean is that on land and at launch the boat starts immediately after button is pushed. After it been driven, shut off, and sat for a while it takes several cranks to start. It doesn't seem to need throttle, bit sounds a little starved (weak) until it idles for a minute.

 

[timmyboy76]

did you go thru/check the accelerator pump/s?...check to see if tank is venting/

 

[lilngineer]

I used the OE Mikuni full rebuild kit and changed all the diaphrams and check valves including the pump side. I also was careful to install in correct orientation with blue lines

 

[timmyboy76]

my mistake..

apologize, thought your boat, had the accelerator pump, built on the carb, besidesthe fuel pump, that is bolted on carb.
Did you pull choke, see if that helps, soundsthough, the "pump" aint pull'n gas...make sure the "pulse" line is clamped, check return line for blockage, inline filter, and.or change the o-ring in the in-line filter...

 

[lilngineer]

Choke doesnt seem to help.

I did clean the online fuel filter and cup, but I will check the seal. I will also take a look at the return line.

If the pump wasn't pulling, wouldn't I have a problem at WOT or on land also?

 

[lilngineer]

Trying to revive this thread since I still have the two problems.

I have tried replacing the needles and seats, return springs and checked the return and vent lines for blockage. Everything seems fine.

Could this still be a low speed mixture adjustment problem? Per the service manual, mine are set at 1 turn out.

 

[glenwhitt]

try 1/4 turn out more on the low speed one and see if it helps.

Do you have pop off guage? You can check and see if the n/s is holding also. if not it will leak down as you sit for a minute or two and cause hard starting. leaking n/s will cause flooding though. You sound lean.

 

[lilngineer]

I had the carbs apart yesterday again and measured the pop-off. 32psi on both carbs.

Originally I had the low speed set at 1-1/4. Didn't seem to help.

I also tested the needle and seat for leak down and it held no problem. The pulse pump also held per the service manual.

 

[glenwhitt]

sounds like you did all the test and they all passed. Only thing I can think of now would be to run the boat like always. turn off and let sit for a few minutes then turn it over a few times, but stop before it starts. check the plugs and see of they are wet our not. if one is wet and the other not then you can focus on the carb.

 

[Gunsrunner]

I dont think there is a problem, in my manual it states, for a cold start, throttle at idle and use the choke once started push choke to half then push in all the way once it will idle. For a warm start do not use choke but push throttle to one quarter to half throttle, once started back off throttle to idle. This is what works best on my boat so to me it dosen't sound like there is a problem.:cheers:

 

[glenwhitt]

If it aint broke, dont fix it. If its broke, replace it

 

[lilngineer]

Could it be rotary valve plate wear?

What about the RAVE valves?

 

[glenwhitt]

not sure what rv plate wear is. Is that the wear in the cover from the rv? no idea if this would cause it or not. You could do a squish test with rv removed with some solder. Specs are in the book. Be ready to find TDC and have a degree wheel when putting back together though.

Never heard of rave valves doing this either. They are the cause for lost rpm's most of the time.