CamH Posted February 14, 2008 Share Posted February 14, 2008 I'd appreciate some troubleshooting guidance and suggestions on a problem I'm having with my round top SU's on my stock L24. I replaced the head gasket on my motor, which was running (blown gasket) when I started the teardown. It was running normally the previous day - an overheating condition (never boiled over or died) tipped me off to the head gasket. After reassembly, I have no start. Engine cranks fine, I have good spark, and I did not do anything that would have changed the timing. My helper and I are pretty sure I have a fuel problem within the SU's. The mechanical fuel pump is putting out a strong flow, and the bowls are getting fuel because they drain fuel when the line is disconnected. When I crank the engine, it spins freely and sounds good, but shows no sign of combustion. When we spray starting fluid into the intake and crank it over, the engine fires. We pulled the plugs after failed start attempts, and they have no fuel on them at all. One person suggested that I try replacing the carbs, but I have a hard time believing that they would have gone bad in between the time they were running yesterday when I pulled them, and today when I put them back on. Any and all help appreciated! Quote Link to comment Share on other sites More sharing options...
Doc Hawk Posted February 14, 2008 Share Posted February 14, 2008 No love on this? Is it that people haven't seen it, or that nobody has any advice? Quote Link to comment Share on other sites More sharing options...
WEBEZEEed Posted February 14, 2008 Share Posted February 14, 2008 You say the plugs are dry, and that the fuel bowls have fuel........ there is not much in between the two. If you had the carbs off check for major vacuum leaks at the gaskets including the balance tube. Quote Link to comment Share on other sites More sharing options...
Doc Hawk Posted February 15, 2008 Share Posted February 15, 2008 I felt the same way... not sure what to point at other than an opening somewhere in the manifold, or some other gross vacuum leak. Quote Link to comment Share on other sites More sharing options...
Dragonfly Posted February 15, 2008 Share Posted February 15, 2008 Pull the dome's off the carbs and remove the pistons, pour out the damping fluid to either re-use or properly dispose of and place the piston's (knowing which one goes to which carb) on a rag with the needle orientated so that it is not hitting anything. Pull your choke so the jets are pulled down as far as they will go then using a good flashlight look into the jet of each carb and see if you are able to see any fuel. If you do not see fuel the problem is between the float bowl and the carb, if you do see fuel the problem is between the jet/needle/piston assembly. It would be virtualy impossible to have a vacuum leak so big as to not pull fuel out of the jet if everything else is ok. Something I have seen many times on these carbs is people using fuel line between the float bowl and the carb that is not the correct line, this will almost always cause a problem in particular (which I have seen before) if someone uses vacuum line in place of fuel line. The vacuum line will break down on the inside from the fuel and it will completely block the fuel from getting to the carb. That whole thing is made even worse if the car begins to run hot. Dragonfly Quote Link to comment Share on other sites More sharing options...
CamH Posted February 15, 2008 Author Share Posted February 15, 2008 Pull the dome's off the carbs and remove the pistons, pour out the damping fluid to either re-use or properly dispose of and place the piston's (knowing which one goes to which carb) on a rag with the needle orientated so that it is not hitting anything. Pull your choke so the jets are pulled down as far as they will go then using a good flashlight look into the jet of each carb and see if you are able to see any fuel. If you do not see fuel the problem is between the float bowl and the carb, if you do see fuel the problem is between the jet/needle/piston assembly. It would be virtualy impossible to have a vacuum leak so big as to not pull fuel out of the jet if everything else is ok. I will take a look at this tomorrow afternoon! Thanks for the advice! Something I have seen many times on these carbs is people using fuel line between the float bowl and the carb that is not the correct line, this will almost always cause a problem in particular (which I have seen before) if someone uses vacuum line in place of fuel line. The vacuum line will break down on the inside from the fuel and it will completely block the fuel from getting to the carb. That whole thing is made even worse if the car begins to run hot. Dragonfly I don't think this part is the problem because it has been set up the same way since I bought the car and I have had zero problems with them so far. Thanks again for the suggestions. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.