| Author |
Message |
'75 308 GT4 (Peter)
Intermediate Member
Username: Peter
Post Number: 1968
Registered: 12-2000
| | Posted on Wednesday, August 21, 2002 - 4:15 pm: | |
Mitch, I'm not sure if you've done this or not, but when installing the wires in your cap, the silicone jacket should be trimmed off and the core exposed. Fold the core over and carefully insert into the cap, making sure the core is facing the screw-hole (check by looking into the hole when fully inserted).
The reason for this is to get a perfect contact with the securing tapered-screw. Piercing the silicone jacket only and you may not get this good contact (or a go-no go contact. Works on the bench, but when moved around, looses contact). |
magoo (Magoo)
Advanced Member
Username: Magoo
Post Number: 3064
Registered: 2-2001
| | Posted on Wednesday, August 21, 2002 - 2:27 pm: | |
Sorry Billy, I stand corrected. |
Lawrence Coppari (Lawrence)
Junior Member
Username: Lawrence
Post Number: 193
Registered: 4-2002
| | Posted on Wednesday, August 21, 2002 - 11:30 am: | |
Last time I replaced sparkplugs one of my vehicles, one plug had a crack in it- came that way from factory. I did not notice the crack when the plug was installed because it was difficut to see. Engine had a cylinder that only fired under no load. The crack was easy to see once the engine was run because crack darkened from leaking combustion.
Crack was axial and ran about 1/8 inch up plug from base. But you would have to have 2 bad ones. Kind of unlikely.
Hang in there. |
Mitchell Minh Le (Yelcab1)
Member
Username: Yelcab1
Post Number: 305
Registered: 11-2001
| | Posted on Wednesday, August 21, 2002 - 10:21 am: | |
The timing thing is a bit of a puzzle to me. With the engine on the dolly, I checked:
1. Compression (got all cylinders)
2. Oil pressure (positive)
3. Static timing at 6 degrees advance on both banks. Set the flywheel to 6 degrees, turn the distributor until the points just crack open and lost continuity on the ohm meter.
So, technically, it should be pretty darn close. But it is not. Oh well.
The carbs linkages are not adjusted at all yet so that is a big part of the problem, I am pretty sure. It is funny when both cylinder 1 and 2 do not fire. They are both connected to the same carb.
The wires thing, I made them up from scratch and measured the resistance before but something may have happend during installation. It is good to check again.
Spark plugs are new, extensions are new, but dist caps and rotors are all old. I did not replace them so I need to look at them more carefully again.
Back to basics is the plan for today.
As for Billy's post, thanks for the technical contribution. That is what this fchat is about. |
Bill Sebestyen (Bill308)
Member
Username: Bill308
Post Number: 320
Registered: 5-2001
| | Posted on Wednesday, August 21, 2002 - 10:17 am: | |
Mitchell, It sounds to me like you're making good, logical decisions and there's no reason to panic. You have spark, fuel, and air to most cylinders. You have oil pressure and the engine will run, so you are in pretty good shape. Is the ignition timing for both banks confirmed to be at 7 BTDC?
For the one plug without spark, this should be easy to trace and fix before restarting.
For the cylinders still not firing, but with spark, are they wet with fuel or dry? If dry, the culprit is likely a very low or no air flow condition on these cylinders, so synchronizing air flows, with clean plugs, will likely bring them back. This is a good time to have an extra set or two of spark plugs, as if they are fouled, which is quite common during initial start ups, you really can't do anything else. If the non firing plugs are wet with fuel, change the plugs with fresh ones and try again. Pumping of the accellerator during the start proceedure could have fouled them.
Try to keep running to a minimum until all cylinders are firing. This will minimize gas washing of the cylinder walls. |
Tom Treue (Treue)
New member
Username: Treue
Post Number: 24
Registered: 4-2002
| | Posted on Wednesday, August 21, 2002 - 8:17 am: | |
Mitch:
Suggest you put an ohm meter on the spark plug extensions and the wires (even if brand new). The extensions should read around 1000 ohms. If they read zero or open, THEY ARE BAD and will not allow proper spark. Check the plug wires from cap contact to the connector that goes over the plug extension. They should also show a fixed resistance, not zero and not open circuit. I had a 308 in which I replaced the plugs. After driving about 700 miles I pulled the plugs for a color check and found 3 that still looked brand new-they had not fired once!! And the engine didn't run that rough. After checking with an ohmeter, I found three bad extensions and at least one bad wire. I replaced all the wires and the extensions that had bad readings (they're fairly cheap)-problem solved, ran smoothly. |
magoo (Magoo)
Advanced Member
Username: Magoo
Post Number: 3059
Registered: 2-2001
| | Posted on Wednesday, August 21, 2002 - 1:28 am: | |
Billy, Your suggestions are welcomed here but Mitchell like a lot of us is a DIY guy. We don't know the problems with the hook but lets not debase the guy for trying. What you suggest is good to help him retrace his steps but knowing Mitchell I don't think he looked at his engine as being just a engine and nothing special. Look at his posts. Obviously you have Tech. knowledge that a lot of us don't have. This is appreciated just don't kick the guy in the ass telling him of his mistakes. You say this is not a put down but it certainly reads that way. Regards, |
billy bob (Fatbillybob)
New member
Username: Fatbillybob
Post Number: 11
Registered: 8-2002
| | Posted on Wednesday, August 21, 2002 - 12:24 am: | |
I have been reading the posts on this rebuild. You need to go back to basics. There is much you think that is unique to the 308. It is just an engine nothing special. The first time you fire up everything should be perfect with very little to know adjustment required. You may want to go back an re-read auto 101. This is not a put down just a suggestion as many of the posts sound a bit extreme like taking the bumper off and breaking the overhead hook to put the engine in etc... You need to go back to basics and really understand how a motor works. Go back to timing theory and make sure all the marks line up with #1 in TDC compression. Then static time the distributors. Until you can guarantee these basic positions you can't start playing with dynamic timing. With only a few cylinders firing playing with timing only compounds the problems. Check all connections in the primary circuit. Next set the carbs up to basic positions without linkages connected. Close idle screws all the way and open 2 turns is a good start. Keep chokes closed. If the car runs on all cylinders then you can tune the dynamic timing per manual specs or your own positions if you are running the R-2 set of points. If you pass there you can now tune the carbs with a synchrometor for flow only. The set the linkages and recheck the flow. If flows are off you need to change at teh linkage not on the carb screws. If you fail on some cylinders and the set up is right for static time and basic engine time then you have to determine if your problem is spark or fuel. If you get a spark at the secondary of each plug and you still have a dead cylinder you have a fuel problem. If you are getting fuel and no spark at the secondary you need to check the primary for spark then each secondary to locate the problems. Just take things in order and think them out logically. |
magoo (Magoo)
Advanced Member
Username: Magoo
Post Number: 3055
Registered: 2-2001
| | Posted on Wednesday, August 21, 2002 - 12:06 am: | |
Hey Bud, I know you did a good job. It probably is something simple but those carbs if not syncd. can give off so many symptomatic problems that you think you have major problems. Just trying to help out. Magoo |
Mitchell Minh Le (Yelcab1)
Member
Username: Yelcab1
Post Number: 304
Registered: 11-2001
| | Posted on Tuesday, August 20, 2002 - 11:59 pm: | |
Yes, Magoo, it did run on all eight cylinders before, that is until the oil line went and then all hell broke loose after that.
During the rebuild, I rebuilt the distributors, the carbs, made up a new set of ignition wires, and changed all the synchronizing setting for the carbs. Today is just a first step of getting back to where I was before the rebuild. Since so many things have been rebuilt (changed), it is no wonder that something is amiss. The carbs were not tuned or balanced at all so I know they really mess me up, but I wanted to quit while I was ahead and it was already a long day.
So, back to basics tomorrow. I know that I have good compression all around, and the crank/cam timing thing was perfect. So other things need to be checked.
Mitchell |
magoo (Magoo)
Advanced Member
Username: Magoo
Post Number: 3048
Registered: 2-2001
| | Posted on Tuesday, August 20, 2002 - 11:00 pm: | |
Mitchell, I may be wrong but didn't the car run on all 8 before the rebuild? Or did you get it in a state of repair? The reason I ask is that cracks in dist caps and wires bad should not be the problem if it was running on all 8 before. Also you say balance the carbs, if possible. They can really mess you up. Especially linkage if you changed anything. To balance them you should first have a synchrometer to get them close and go from there. Just curious. |
George Daina (Oof_n_goof)
Junior Member
Username: Oof_n_goof
Post Number: 104
Registered: 7-2002
| | Posted on Tuesday, August 20, 2002 - 9:43 pm: | |
not familier with the dual ignition, but on single distributor systems, i'd check if distributor is off a tooth, advancing may correct that, also, if valves are set too tight, or heaven forbid, if cam gear and crank gear off a tooth, but I'd check ignition wires first
, then check distributor cap for cracks |
Mitchell Minh Le (Yelcab1)
Member
Username: Yelcab1
Post Number: 303
Registered: 11-2001
| | Posted on Tuesday, August 20, 2002 - 9:00 pm: | |
I buttoned up everything today, filled in some gas, coolants, and an all around check. Then, crank the key.
Mishap number 1: The fuel line from the carb to the tank was not connected so I got a liter of gas on the floor. Wiped it cleaned, connect the line and we are on.
Second try, it turned, turned and turned, and then got positive oil pressure, the oil pump lives.
Third try, it cranked, and popped and then fired up a a low rumble. I got out turned the carb idle up and it runs at 900 RPM.
Then it back fired like mad so I hooked up a timing light and timing was way off. So I adjusted to 7 degrees advanced and it smoothed out and stopped back firing.
But it does run only on a few cylinders so I did the pull the plug wire test to find that
1. There are sparks on all but cylinder number 7 (it may be a broken wire or something)
2. 1, 2 and a few others did not fire.
So, I decided to quit while I was ahead and start fresh tomorrow.
Tomorrow, I will start checking
1. Caps and rotors, and measure out the wires.
2. Spark plugs read and cleaned again
3. Balance the carbs if that is possible
Any other suggestions? |
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