Engine won't fire after rebuild, ideas???

[Kris]

HI

Iv just finnished rebuilding my 1600 twin port stock engine after the big end bearings disinteated on my way home from Cornwall. My problem noe is that my rebuilt engine will not fire into life and shows no signs of doing so.

I think my problem may be fuel related as i have a good spark on all of the plugs, which are new and have replaced the distributer and coil. the timing has been checked and rechecked and is set correctly. however there don't appear to much, if any fuel finding its way to the spark plugs, although there is fuel from the pump to the carb. the carb was working fine before the rebuild, and no changes were made to the settings, although that has since changed, but to no avail.

I have been wondering if there could be a problem with the manifold? it does'nt have any visible damage, holes or blockages though. The manifold that i am currently using is a different one to that i was using originally as i found one of the ends, which attache to the exhaust was blocked.

I would be grateful for any advise on what the problem could be!!!

many thanks

 

[Araon]

youve pulled the filter and had a look at the fuel being injected into the barrel?

your manifold rubbers are in tip top condition?

new gaskets to manifold/heads?

are you sure the fuel pump diaphragm are in good order and not failing when under load?

all quick and easy checks which will hopefully steer you in the right location....

 

[Kris]

I have replaced the rubber seals on the manifold and used new gaskets, and checked all is tight and as it should be. ive also removed the air filter and checked the fuel is being injected into the carb, so im sure the fuel pump is fine as i can see fuel squirting from it when the engine is turned over.

thanks for your surgestions, if you can think of any others i would be very grateful.

 

[mk2matt]

not dissin you dude but have you tried to put dizzy 180 degrees out?

sometimes this will help and you might need to rewire the leads to suit.
i found this out on mates bug, the dizzy spline can be put in 180degrees out, my mechanic mate told me it gets quiet common

 

[Slammed]

Have you reset your valve clearences? If you've had the bottom end apart they could now be miles out, even if you put everything back as it was. 8)

 

[Kris]

yep have checked and rechecked the valve clearances and have replaced and adjusted the points. i have also tried an electronic ignition instead of the points.

thanks for your help, please keep your ideas coming!

 

[richbaker78]

have you got a decnet starter and battery. i had the same problem...fuel and spark but starter was turning over but just not enough to get it to fire (it sounded ok but wasnt until a new starter you could se the difference) in the mean time i ended up tow starting it.

does sound fuel related though...have you checked fuel in the float chamber and is there any fuel on the plugs?

if leads / timing is out you would at least expect a backfire.

Assume you also have good compression? have you tested...one of your heads might be leaking or summat.

 

[Kris]

It has a new starter motor and i have tried boosting the power a little when turning the engine over. this did seem to help the starter motor although the end result was still the same, it did'nt fire up.

the plugs however don't appear to be getting any fuel in pistons 3/4 and little in 1/2, although it can be smelt they are not wet even when i would have expected them to be flooded.

I have checked the float chamber which has fuel in it. i have also checked the pilot jet, which is clear and fuel is getting from the chamber through the injection pipe from the accelerator pump. i have noticed on inspection of the carb, there is a small crack in the plastic gasket between the two seals, where it attaches to the manifold. the crack does'nt appear to go all the way through. i have also noticed that the rear connecting nut on the carb does'nt appear to tighten unlike the front nut, which tightens up as normal.

 

[richbaker78]

Assuming that everything is in order as you suggest above re timing etc If you have what seems to be a correctly functioning carb...but your not getting fuel through then it sounds like you have a big air leak....ie there is no suction at the carb to draw through enough fuel. Do you have a servo take off on your inlet manifold? if so make sure its blocked/ connected. Check there are no other major air leaks.

get a friend to turn it over whilst you open the carb butterfly and spray in easystart/ carb cleaner....(lots of it) hopefully your engien will fire momentarily so you can discount things like compression / ignition and start investigating the fueling further - ie if its carb issues or airleak issues.

 

[chrisby]

Try pouring some fuel down the top of the Carb,it worked for me after renewing fuel lines.

 

[Kris]

Hi, i have tried putting fuel directly into the top of the carb, which had no effect whatsoever. i do plan to change then carb when i get chance to see if that has any effect. however, im not totally sure it will as my current carb was working fine before the rebuild. Apart from the banging due to the warn bearing and crank, the engine still started ok and ran in idle before the rebuild.

thanks for all your help