atkinson40 Posted July 11, 2009 Report Share Posted July 11, 2009 Picked up a 1972 Datsun PU yesterday for $200. It won't start. Previous owner said he let it overheat. I charged the battery and tried to start it. Wouldn't fire up. Poured gas in carb and no change. Pulled wire off plug and had wife turn over while watching spark from plug wire. Before I start tearing things apart I'm going to pressure wash today. I pulled the dipstick and don't see signs of water in the oil but do smell a faint gas oder coming from the radiator fill. How do I tell if the head gasket is blown? Thanks Kevin Quote Link to comment
banzai510(hainz) Posted July 11, 2009 Report Share Posted July 11, 2009 I would try to get it running first. see if gas shoots in the carb, if not the carb is not filling with gas. Either needle valve on carb is not letting gas in or fuel pump is not dleiving gas. Since you poured gas in it should at least fire/pop/backfire or something. Now look at the points/condensor. coil wire. Make sure you have power to the coil. also make sure when key is in "START" that you get 12volts also. this is the hot start bypass. make sure the distributor is lined up also at TDC and plug wire point to #1 plug wire. and make sure its 1 3 4 2 fire order counter clock wise. http://www.guba.com/general/search?query=hainz&set=5&x=0&y=0 Quote Link to comment
atkinson40 Posted July 11, 2009 Author Report Share Posted July 11, 2009 It has spark at the plug wire when my wife turned it over so I assumed the electrical was OK? Previous owner said it was his daily driver until it overheated and he couldn't get it started. When I poured gas in the carb I got no pops or attempts from the engine to fire. With spark and gas I would have at least expected that. Also if there was a blown HG I would have expected the moter to at least try to start and maybe start and blow steam out the tail pipe, but I get nadda. Thanks Kevin Quote Link to comment
Bugeye Posted July 11, 2009 Report Share Posted July 11, 2009 next step for me would be a compression test Quote Link to comment
banzai510(hainz) Posted July 11, 2009 Report Share Posted July 11, 2009 Bugeye is partial correct. before doing this compression test make sure the valve lash is OK. If the rockers are tite up against the cam lobe the compression and gas mixture blow right out and not even FIRE. when cking for spark you used the center wire from the coil to ground I assume? Quote Link to comment
ggzilla Posted July 11, 2009 Report Share Posted July 11, 2009 Yer Haines as usual is right. But is much quicker to do a Compression test. If it reads good, then it's not a problem with valve lash. If it's not good reading (all 4cyls with 10 psi of each other) then you can check if is valve lash or something else. You can't really confirm if it is a blown head gasket by compression check alone, but if the compression is good, it should start. Quote Link to comment
banzai510(hainz) Posted July 11, 2009 Report Share Posted July 11, 2009 well I say lash ck cause its FREE I bet most new Datsun owners dont have a compression cker or timming light! Quote Link to comment
Bugeye Posted July 11, 2009 Report Share Posted July 11, 2009 well I say lash ck cause its FREE I bet most new Datsun owners dont have a compression cker or timming light! true, the first things I always do is a cylinder leak down, check the valves then the compression (if it has spark) I think it should be required if you own a datsun to have a timing light and compression tester :lol: Quote Link to comment
ggzilla Posted July 11, 2009 Report Share Posted July 11, 2009 Good idea, checking lash can be done without special tools. You don't even need a feeler gauge if you are just verifying that there is some clearance. Quote Link to comment
atkinson40 Posted July 11, 2009 Author Report Share Posted July 11, 2009 After charging the battery over night I was able to get the engine to run. It took some cranking and mucho pumping on the gas pedal but it finally started. It will stay running fine at high idle but wont low idle. When it's running there's a ton of steam belching out the exhaust pipe, and I see a rusty water patch underneath the exhaust where it spit out stuff that I imagine came from the radator. I'm really thinking blown HG now. From the sequence the previous owner told me.... It was running fine. He forgot to put in water and it overheated. Then he couldn't get it to start. Am I going to need to resurface the head or do I have chance of just replacing the gasket? TIA Kevin Quote Link to comment
ggzilla Posted July 11, 2009 Report Share Posted July 11, 2009 Rarely do you have to resurface a Datsun head. Check it with a straightedge, it can have up to 4-thousands from flat (0.004 inch). Careful prep (cleaning of gaskets faces and head bolt threads) is the key. Quote Link to comment
Guest kamakazi620 Posted July 12, 2009 Report Share Posted July 12, 2009 i've done headgaskets before keything is TAKE YOUR TIME clean gasket surfaces VERY well GOOD LUCK and WELCOME to RATSUN!!!! Quote Link to comment
banzai510(hainz) Posted July 12, 2009 Report Share Posted July 12, 2009 make sure the intake is also tight as the passages can suck water in if the intake gasket is cracked. But looks like it could be bad head gasket. I would pull head and remove the rocker arms and se eif can can spin with your hand. If yes then the cam is not binding(meaning head twisted) and maybe you can get away with a slight milling of the head and a head gasket swap. http://www.olddatsuns.com/620tech.htm timming chain install video,watch it!!!!!!!!! Quote Link to comment
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.
Note: Your post will require moderator approval before it will be visible.