'76 out of the shop, with issues

[drovak]

Hi everyone!

It's been a while, but I was able to get a lot of work done on the '76 this winter. I had the firewall professionally welded up around the clutch cable, and that seems to be holding marvelously. I also replaced the front springs and shocks. I had done the rear a few months ago now. The car is now sitting very level and looks great. I also got some Maserati Biturbo wheels from Csaba (thanks again!) and had them blasted and powder-coated. They look okay, but the blasting shop did a terrible job getting the chrome off. Oh, well...live and learn.

I am having issues, of course. Firstly, I don't have any headlights. They were working fine before, but not any more. Fuses checked out, but I haven't delved into any more than just that.

I also am not running on cylinder #4. I checked the compression on all four cylinders, and from 1 to 4, I'm getting 94 psi, 89 psi, 61 psi, and 60 psi. This seems quite low, but it should still do something on #4 even with that compression. Spark plugs look fine, and they are definitely firing. I have dual 40 DCNF 12 Webers, so I'm thinking I now have a clogged jet going into #4. Getting that carb off is the biggest pain, however. Anything I can do without taking the carb completely off? I think I'm going to get a can of engine starting fluid (if I don't have any right now) and spray it into that barrel to see if it does run at all (I'm expecting it will).

Any tips would be greatly appreciated. This car should be back on the road soon!

Check out some of the pictures of the repair and other various things here.

Kyle

[manoa matt]

Any head lights, or just no low beams? Try the high beams and see what happens. Check that you have good grounds at the ground pods attached to each inner fender near the front of the engine bay. The contacts on the column switch could have burnt out. You have to remove the steering wheel and the column switch assembily to check. Look at the bottom where all the wires are riveted to the plastic plate. Check for a melted area. The solution is a new column switch and to add relays to the headlights so they get power directly from the starter or alternator instead of through the column switch. Do a search for "headlight relays" for how to wire them in.

You have low compression on both #3 and #4, which could indicate a blown head gasket fire ring between the two adjacent cylinders. One easy way to check is remove all spark plugs, turn the engine over by hand so all the timing marks are lined up. The #4 cylinder will be on the compression stroke with its valves closed. Take a length of hose and stick it over the spark plug hole and blow in the hose, listen near the #3 plug hole to see if you hear any air transfering over.

If you have an air compressor and a blow nozzle with a rubber tip even better. Just keep the pressure below 10psi or you can force the piston down and start the engine rotating.

[drovak]

No headlights at all. I have horn and turn signals, but I don't think I have wipers either. I'll have to check on that tomorrow. Again, it was certainly working fine before I had the steering column out to do the welding on the firewall, so maybe it's just a bad connection somewhere.

Thanks for the tips on checking the head gasket. I'll certainly give that a try this weekend. I'll also have to figure out why #4 isn't getting gas.

Kyle

[So Cal Mark]

a cylinder with 60 psi won't fire at idle. It may do a little at higher rpm, but your numbers are very low across the board. I'd verify the cam timing is right. You need at least 100psi for a cylinder to function

[drovak]

Interesting. Cylinder #3 fires (as do #1 and #2), and yet it has the same pressure. I'll get some ether and try spraying it into #4 to see if it makes a difference when it's running.

Kyle

[sptcoupe]

I think with those numbers across the board you have one of the issues the guys have already mentioned. But assuming it is only a carb problem you probably have a blocked idle jet on the bore. Just unscrew it, clean it out with carb cleaner and squirt the carb cleaner into the idle jet cavity ans ee what happens. The idle jets on a DCNF are easy to get to and clean with the carb on the car, and require no dissaembly. The are located near the top of the carb, on the sides, between the bore and the float bowl.

[jkn070458]

A carb jet has nothing to do with this issue. As stated by some compression is low on all cylinders. How did you perform the compression test? Here is how I do it in my shop. First disable ignition and fuel, second remove all spark plugs. Next smash the gas pedal to the floor to obtain wide open throttle (WOT). Make sure that the battery is fully charged. Connect the compression gauge to each cylinder, crank and observe pressure until it tops off (4-5 cranks should be good), record results. Next perform a wet compression test. Squirt oil into each cylinder and crank to distribute oil onto the rings. Crank the engine as described above. Compare findings for a clue. Poor compression may be caused by various issues. Out of timing, worn rings/cylinder walls, coked up valves etc... These engines need the basics, fuel spark and compression. Good luck!

[manoa matt]

Dovak posted this in another thread, I thought it would help diagnose or resolve his problem:

"And in other news, I was able to get the car back operating on all four cylinders. I just cleaned the jets going to cylinder #4, and that cleared it up. It's still backfiring every now and then, so I'd say it still needs a good tuning. I did open the gas needle valves a bit, which seems to have helped some."

[drovak]

Thanks for that, Matt. It's always good to have a resolution to a problem so that people down the road (pun definitely intended) can learn from our experiences.

Definitely one of the most troublesome things to see, especially on the Linux forums, is "I have a problem!" "Oh, never mind, I fixed it." without describing what the solution was.

Kyle

[gwb]

If you have the Alquati manifold like mine, you will not be able to get it off without taking the head off with it. Your DCNFs are mounted opposite to the way mine are mounted, so that probably makes it tougher for you to take them off alone.

Out of curiosity, what are your jet sizes? I have 42DCNFs, but I could list the jettings if it'd be useful to you. If you really want to get the car running right with those carbs, you could easily get a shop to weld an O2 bung to your header and you could wire up a rich/ lean indicator to aid you in tuning.