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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: devanray on March 10, 2011, 11:05:07 am
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77 C-10, 350 with a 400, unsure of gearing, 1980 Rochester Quad.
The truck starts up fine first thing, but it seems that after the engine gets warm it will just crank and not actually turn over. I have to really give it some gas, to the point of flooding it before the engine catches and then it is all 'boggy' because of the amount of gas I've given it. Here is a real life example:
Started fine, drove for 10 minutes @ 45 mph, shut it off, five minutes later it started with no problem, drove for 35 minutes @ 55-60 mph and shut it off for 20 minutes, wouldn't start.
Different day; Started fine, drove for 5 minutes @ 35 mph and shut it off for 10 minutes, started up, drove it 1 mile @ 10 mph (crossed the street) and shut it off for 5 minutes, wouldn't start.
Any ideas? I don't even know where to start, seems somewhat random.
Thanks in advance
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Today she had trouble starting first thing. When she did start white smoke blew out from the exhaust. I have also noticed the other day the level in the fuel filter had dropped, it still started fine then, but shouldn't that level be the same always?
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do you have any pictures of the filter when it is running, it may be getting low fuel pressure when it is hot cause of a bad pump or maybe a restriction maybe?
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I'll see if I can get a shot of it after running for a bit (tomorrow). I was thinking fuel pump might be an issue as well, any good way to test?
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I had the same problem with my 79 a few years back that when I drove it, then turned it off for a minute or two, it wouldn't turn back on unless it sat for 20 minutes or so. It always turned on just fine when the engine was cold. It was the module in the distributor that went bad.
You can also check to see if your choke opens all the way after two minutes of driving. When you restart a warm engine, the choke should be open all the way.
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I had the same problem with my 79 a few years back that when I drove it, then turned it off for a minute or two, it wouldn't turn back on unless it sat for 20 minutes or so. It always turned on just fine when the engine was cold. It was the module in the distributor that went bad.
You can also check to see if your choke opens all the way after two minutes of driving. When you restart a warm engine, the choke should be open all the way.
Was it an HEI? I only noticed this issue after I took the cap off to plug in the tach. I really didn't think it would be the cause but more just a coincident. How did you figure out that it was the distributor module?
I'll check the choke as well (tomorrow when the rain and winds die off), its an electric and wasn't hooked up when I bought this rig, maybe thats why. Umm... whats the best way to check it, on the four barrel, does it open the primarys when "the choke is open all the way"?
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I had the same problem with my 79 a few years back that when I drove it, then turned it off for a minute or two, it wouldn't turn back on unless it sat for 20 minutes or so. It always turned on just fine when the engine was cold. It was the module in the distributor that went bad.
You can also check to see if your choke opens all the way after two minutes of driving. When you restart a warm engine, the choke should be open all the way.
Did you finally check the module? I thought you said you were pretty sure it was the pickup coil. . .
http://forum.73-87chevytrucks.com/smforum/index.php?topic=9335.0
You have to pull the module out of the distributor to have it checked at the parts store. Although, if your choke isn't hooked up to B+ but you still have everything there, that can cause some problems.
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Texas, you are correct, it probably was the pick up coil, sorry. It's been a few years and at my age, memory becomes fogged. It's easier for me to just replace the whole distributor since I have so many and they are cheap at salvage yards.
Yes it is an HEI.
Checking the choke is easy. The top flaps are either open or closed after you activate the accelerator. They should be open when the engine warms for a few minutes. They should be closed when engine is cold and hasn't been run for a while. I guess there is an in between (half open, half closed) if the engine is a little warm perhaps--but i like to simplify the concepts so its easy to understand.
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could it be the starter is getting to hot??
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Don't think it is the starter, she cranks up just fine. I'm thinking that it has something to do with ignition or fuel. I'm not used to HEI so I don't have a clue how to test the coil either, can an autoparts place test the module and the coil?
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could it be the starter is getting to hot??
Could be if its caked in mud
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The starter is clean, if it were to hot than it wouldn't crank, right?
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Next time you have the problem of it not starting, check for spark at the spark plug. A bad pickup coil will make it so you have no fire (spark) at your spark plugs.
I'm not used to HEI so I don't have a clue how to test the coil either
Remember, you have two coils in the HEI distributor, the actual "coil", which has 4 little screws.
(http://www.msdignition.com/uploadedimages/MSDIgnitioncom/Products/Coils/8225_full.jpg)
(http://www.fordmuscle.com/archives/2004/09/DUIdistributor/images/coil_md.jpg)
and the pick up coil which is further down the distributor, a ring shaped gizmo with a wire...what you describe sounds like a problematic pick up coil to me, if you don't have spark when engine is hot...
(http://www.go2marine.com/go2_structure/7/6/3/1/76315F-p.gif)
http://www.youtube.com/watch?v=z47TliL4OJ4 (http://www.youtube.com/watch?v=z47TliL4OJ4) testing spark for pickup coil.
could it be the starter is getting to hot??
If that were the case, the starter wouldn't even turn. It doesn't sound like that is the problem.
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I suppose now is as good of a time as any to get to know an HEI. I'll take it apart tomorrow, this can be done pretty quickly with the dist still in the vehicle right? Doesn't look to tough to take the HEI coil out but how much farther down is the pickup coil? This should be fun.
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need to figure if your fighting fuel or fire. I keep a good spark pkug handy when trouble shooting things like this. Whe it refuses to start, pull a plug wire off, put the plug in it and lay it so it will ground out against engine block. Crank it over and listen for tick ( spark sound can some times be heard) or it is better if you have someone crank it for you while you look for spark. I wouldnt hold the plug while cranking because its gonna hurt. Some people do know that, im not meaning to indicate you dont. Just in case tho. If you have spark, then its possible a fuel problem. I had ha 68 Elky that had some similar issues after a header install. My inline fuel filter, similar to the one you showed but mine was metal, was getting hot causing the fuel to vaporize once it got to the carb. I relocated the filter further away from the headers and all was good. Also had a motor home with a 454 doing a similar problem and an older mechanic wrapped the fuel pump in tin foil as a heat sheild. Problem solved.Just some thoughts.
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Doesn't look to tough to take the HEI coil out but how much farther down is the pickup coil? This should be fun.
You can't change the pickup coil while the distributor is installed.
http://www.youtube.com/watch?v=K5QRK9VZwcM&feature=fvwrel (http://www.youtube.com/watch?v=K5QRK9VZwcM&feature=fvwrel)
http://www.youtube.com/watch?v=pjivERnPWHw&feature=relmfu (http://www.youtube.com/watch?v=pjivERnPWHw&feature=relmfu)
not an HEI, but you get the idea.
this is interesting to test HEI...
http://www.youtube.com/watch?v=ufSoBODtk9Y&NR=1 (http://www.youtube.com/watch?v=ufSoBODtk9Y&NR=1)
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Choptop; great thoughts. I wonder though if that also would effect performance while driving the vehicle, I've had no problems while it is running, only starting after it warms a bit. And safety tips are ALWAYS welcome. Hope for the best, expect the worst and assume nothing.
I've got new plugs so I'll run some errands tomorrow and wait for it to not start and then check for ignition spark.
SgtDel; replacing that pickup coil looks easy enough, a bit time consuming but not to viscious, haven't finished watching the second vid yet though. That last vid I have actually seen and it makes sense but how would I heat it up? Don't have a heat gun anymore, could use my popcorn popper I suppose :D
I'll just test her in the rig for now, probably get wrapped up in a straightjacket if I were caught pointing a popcorn popper and an engine part :P
So, tomorrow I will wrap the fuel filter in foil (what the heck right?), pull a plug wire and test for spark when she refuses to start. I'll have the modulator tested and post results.
Fighting Fuel or Fire, I like that.
Thanks all, I truly don't know what I would do without all of your help, except spend tons of $ paying mechanics to guess at what the problem is. So far I've been to two mechanics and it was a waste of time, one told me to get a bracket and a detent cable, this forum taught me that a THM400 doesn't even use a detent cable, just the solenoid and the kickdown switch.
Transmission diagnostics = $150
Engine diag and tune = $170
73-87chevytrucks.com = Priceless
(to be honest, I haven't spent a dime on the mechanics diagnostics but still....)
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I could not duplicate the issue today, I did change the plugs this morning while the engine was cold and tested spark with no issues. Idled for 15 minutes and drive for 10, electric fan kicked in so I know temps hit at least 185 degrees. The truck started up every time with no hesitation.
Fuel filter level was almost full this morning and after the drive it went to the red line level in the pic (normal).
Going to go for another drive and get an oil pressure gauge. I'll update if anything changes.
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Next time this happens check your power wire (red) that goes to the cap with the key on. Then check it with someone trying to start the truck
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I will do that, yesterday was pretty cold out but today is a bit warmer so I may have a chance to do this. I can't imagine replacing plugs would have solved my issue. below is a few shots of the plugs I pulled out.
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I don't see anything unusual with the plugs. Gaps??? The hot fuel issue only showed itself when shut off on a hot day and it sat for 10 minutes or more. If it shut off and immediate restart, no problem occurred. It had to sit long enough for for everything to get hot. As long as fuel is flowing it wouldn't get hot enough to vaporize
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Actually the gaps were different, I noticed that the gaps on the new plugs (pregapped) were larger than the old ones. Your symptoms are on the nose with my issue. Ran it on a hot day yesterday and had a tiny amount of issues (compared to before the plug replacement) starting her up. The spark checked out fine, as well as the power to the distributer. I want to say that vaporizing sounds like a good probability. The fuel filter is about a foot and a half away from the exhaust and has never felt even warm. I still smell fuel and exhaust when exiting my vehicle on a hot day, going to get my coal canister hooked up to the carb soon and see if any difference is made. The exhaust smell may just be normal for a 34 year old vehicle.
How does one take care of vaporising fuel?
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if you wana test for vapor lock then when it acts up again spay starting fluid or carb cleaner into the carb and see it starts. Just to clear up something when it does act up it won’t start at all right? Or does it run rough or what?
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IMO this sounds most likely a coil problem.
you can test your coils by checking for resistance. I don't know the specs but if you have some spare dist laying around you could compare the readings or just look them up somewhere.
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I wish I had spare parts of this or that, but I live in a town-home and do all of my work in a parkinglot, pretty much sucks. But, I'd rather work on my 1977 C 10 in a parking lot than my wifes 2005 Ford Escape in a garage ;)
When the vehicle acts up it will not start for about a minute or two before it comes grumbling to life, sputtering white smoke and needing way to much gas pedal to keep it alive. When it gets over that, about 30 seconds or so, it goes up to normal rpm and acts like she should, no problems ever while driving. Just like what ChopTop saidThe hot fuel issue only showed itself when shut off on a hot day and it sat for 10 minutes or more. If it shut off and immediate restart, no problem occurred. It had to sit long enough for for everything to get hot. As long as fuel is flowing it wouldn't get hot enough to vaporize
I will have to look up testing coils and find some other data to compare, but honestly, It may be the answer to just get a module and pick-up coil and just rebuilt the dist. The price though comes close to a new one, about $30 diff. What advantage would a new one have over just 'rebuilding' one?
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So its not that it wont start at all just like its getting to much. If its vapor lock it will start only after the fuel cools down.
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Ive got two 60 year old vehicles and neither one have the fuel or exhaust smell when i get out, but that does bring something to mind. check the hoses to your inline filter to see if the clamps are loose or if the insides of the hose are cracked. If you smell gas, its not for a good reason. Also if you have an exhaust leak on the right side it will cause alot more heat on that side. Make note of how close the hard line from the fuel pump to the carb is. If it was replaced by a non factory line it may be rerouted to close to the exhaust as well. Also make sure there arent any signs of fuel leakage around the carb. I actually had a QJET years ago that was acting weird. Saw signs of fuel leakage and found out some of the screws were loose on the carb. Tightened them up and all was well. The guel smell could be the vent not being hooked up to the charcoal canister, but I havent experienced that as an issue. I think f you find the source of the fuel smell youll find the main issue. Gas smell is vaporized fuel, which is hot fuel. Good luck.
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It's been a few days since I've had the chance to dig around and follow tubing, but I did drive it yesterday (80 degrees out) and did not have the same issues as before. To start when engine is warm I would just put the pedal down and turn the key, she would crank for a bit and then vroom to life, I slowly let of the gas pedal and she seems fine. I still think I'm having some sort of fuel issue though. I'm going to keep checking things out and see what the fuel pressure is like. How do I test fuel pressure anyways?
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you can go the the auto store and get a inline fuel psi gauge. I have one and it works just fine.
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I'll do that, I'll have to save up some cash since I am already WAY over my budget for this rig. Inline gauge sounds good though, will always be able to see what is going on.
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spectre makes it. I dont know what carb you have, but I used PN 29883 and 59013. I didnt need 29883, but it does have the fitting for the gauge and it insures the gauge wont move around from hose flex.
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Fancy web site. I bought that unit from Amazon, I'm on that 'Prime' trial thingy and get free shipping so... ALso got a book on the Rochester Quad just to make sure all is good there.
Now... Must... Put... Away... Wallet..... :'(
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Put in the Spectre fuel pressure gauge, after the pump, used teflon tape and made sure that there were no kinks. When I started the truck (cold) the gauge was bouncing from 4 to 7. The bounce was fast, could hardly see the needle. After the truck warmed (10 min @ idle), it was bouncing from 1 to 9, the bounce would broaden in range when I would accelerate, 0 to 12 (hard to tell, it was bouncing so fast) now after some revs and another 10 minutes the needle finally settled to 6 and drop to 5 or 4 with slight revs (the drop is from less backed up pressure because the carb is pulling in more fuel?).
Is this initial bounce thing normal? I'm letting the truck cool and will start her up again to see if the bounce is back. From what I've read the steady 6 reading sounds like a good place to be, right? ((Roch Quad w/ mechanical fuel pump)) Also, I took the carb fuel filter out and it looks kinda dirty but I'm not sure what it should look like, anyone have any pics of a dirty carb fuel filter (what is this one called) and a clean one?
Thanks again!
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gas will eat up the teflon.
the bouncing could have been caused by a air pocket.
6 psi is good.
if the filter looks dirty, then clean it. is it discolored, or are there particles?
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Should I take the teflon off?
Some particles, the color is hard to say, its darker brown than the pic I found online of a new one.
How do you clean a fuel filter? Carb cleaner or something?
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A new filter is only about $3.