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1984 Chevy G20 5.0L starting issues

Hello!

I’m having trouble with my van. The battery is good (new AGM), starter is good (replaced about 1.5-2 years ago), and I definitely have fuel in it.

The starter will crank, but no matter how long I do it or how much I pump the gas or use the choke (I’m assuming the little black pull-out knob to the left of the steering wheel is the choke, but haven’t really ever had to use it in the past and can’t find images or notes in the manual to confirm that it is indeed the choke), the engine will not turn over.

I would like to try to get it running myself, but I don’t really have anyone with more engine experience to guide me. So, here’s what I’m thinking the potential issues could be (in no particular order):

carburetor
fuel filter
spark plugs/ignition coils

My question is which order should I approach these and is there a good way to diagnose the problem through functional tests, etc.?

I don’t have a lot of money, so I want to pay someone to fix it as a last resort and would prefer to approach the issue as cheaply as possible. If there is an additional component that could be the problem, what is it? Is there something up above that wouldn’t likely cause the problem I’m having?

Thanks,
Trent

Edit: Additionally, I didn’t really find it dead… it just got harder and harder to start over a period of about a month or two. Had to pump the gas more and crank the starter for longer until one day it wouldn’t start at all.

Have you checked the fuel filter?

Check for spark.

If there’s no spark, the problem might be with the ignition control module.

https://www.rockauto.com/en/catalog/chevrolet,1984,g20,5.7l+350cid+v8,1045842,ignition,ignition+control+module+(icm),7172

Tester

Cranking IS “turning over” You just can’t start it. An engine needs 3 things to run. Air, Fuel and spark. I’ll assume the basic mechanical are all OK.

Remove the air cleaner, is it nasty dirty? Try and start the engine. Won’t start? Next…

Look in the carb with the engine off, open the throttle quickly. Does fuel squirt in? No? Change the fuel filter. Try again… Yes? Got fuel, next spark.

Remove on plug wire from the plug, stick a screwdriver in. Hold the plastic handle and get the metal shank close - 1 mm should do - to bare metal on the engine. Have someone crank the engine over. Got spark? If it has fuel, that is likely a No so I’d suggest a coil has gone bad or the ignition module.

This van should NOT have a manual choke. If it does, it has been added by a previous owner. If you’ve never needed it, the engine likely runs rich and gets 9 miles to the gallon.

Post back with what you find.

An engine needs four conditions to run.

Air, fuel, spark, and COMPRESSION.

Tester

Which is why I wrote;

Trying to keep it a little simpler for the OP because of;

Maybe the engine won’t start because the timing chain jumped time?

Tester

Let the guy check fuel and spark and post back. If it was a 70’s Pontiac or Buick, I’d say it was pretty likely. A Chevy, not so much unless it had serious high miles… but he didn’t tell us anything about that.

Manual choke in an 84? I dunno, first thing would be taking the air cleaner off and seeing if that knob actually activates the choke. Then seeing if there is any gas in the carb, along with seeing if there is any spark at the plugs. Not to be difficult but if we don’t know what that knob on the left is for, maybe a little library time first in the repair manual section would help.

Agree about the manual choke it might be possible but I have never seen one one the left side of the wheel.

If the van was running OK then suddenly won’t start and has less than 200k miles on it and you just want to skip through all the diagnostic trees here are the apparent most likely causes of the “crank but won’t start” problem beginning with cheap/easy .

The fuel filter is in the carburetor. To remove it you must hold the large fitting nut while unscrewing the flare nut, then remove the fuel line, then the large fitting nut then the filter will be hanging out the hole. A spring is in the hole beyond the filter. Pay attention to how the filter and spring are installed.

Possibly the fuel pump failed. look under the passenger side of the engine a few inches above the pan to see the pump. There is a ‘weep hole’ that will have fuel dripping out if the pump has failed. Removing and replacing the pump is obvious but getting the pump push rod on top of the pump lever can be a pain.

failed ignition module which is easily accessed and replaced on a van. Mark the plug wires to the passenger side plugs in order to replace them in the proper pin on the cap before removing the cap and closely inspect the cap and rotor for carbon flash which can trash a new module. The modules are inexpensive and quite reliable but if the rotor is badly carbon tracked it is likely that the pickup coil and module are shot and the distributor must be replaced to change the pickup coil.

Small block Chevrolets are prone to jumping time but with average maintenance they usually run beyond 200k before failing. When they jump the sound of the engine cranking has a distinctive sound indicating no compression.

If you don’t want to waste time and money having a shop diagnose it throw some money at it. Good luck.

Also, back to the top, there are 3 fuel lines on the pump. One is metal going to the carburetor. Two are rubber, the larger rubber line is fuel from the tank and the smaller is a return line to the tank through a pressure relief valve which can stick open and result in the pump pushing all the pressure back to the tank. If no fuel is leaking out of the weep hole remove the small rubber hose and crank the engine a few seconds and if fuel has run out the pump is working and you can reconnect that hose and pinch it off in case the pressure relief is the problem. If so the engine should start.

Maybe a vent if the vans still had them.

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Engine needs 5 things: air, fuel, spark, compression and timing. Just being kind of a smart alec but this is the order of diagnostics.

That would include ignition timing.

Tester

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Thanks for the help, everyone. I haven’t had a lot of time to work on the problem yet, but I did do a couple things today. I replaced the air filter (it was pretty nasty) and I pumped the gas pedal to see if I could see fuel. Only thing is, I didn’t really know where to look. I assumed I should be looking down through the throttle plate, which is what I did, but I couldn’t see anything from the angle that I was looking from. The engine, as you probably all know, is kind of tucked under the dash, so it’s not super easy to see. Would it be obvious? I could definitely smell fuel, but that could just be residue or whatever.

I guess I should’ve mentioned that it still wouldn’t start after the air filter change. I’m sure it’s probably due for a fuel filter change regardless of whether or not that’s the actual cause of the problem I’m having. I’ll probably swap that out and then replace all of the plugs, just for the hell of it. Then I’ll give it another crank and see if that helps. After that, I guess I’ll try to get it towed to a shop. Probably better to do that then waste my time and money tinkering around when I don’t really know what I’m doing.

Also, for the inquisitive minded:



That black knob look’s to be aftermarket maby for an added on item or fog light’s that was added on somewhere along the line over the year’s.

Oh, interesting… I never thought about it being connected to lighting. I’ll have to check that when I get a chance. It has a towing setup, so maybe it’s connected to that somehow.

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Spray a small amount of starter fluid into the air intake to see if that gets some life from the engine. If that doesn’t help at all then you need to check the ignition next. If the ignition is working then you need to check the compression and valve timing.

Usually this sort of problem is either not enough spark or not enough fuel. Usually I start with a spark test. I’ll connect a spare spark plug to one of the spark plug wires, hold the plug against a good ground far away from any fuel source, and ask a helper to crank the engine while I see if a whitish-blue spark jumps across the gap. If that tests ok then the problem isn’t spark, so next I’ll reconnect the spark plug and spray starter spray into the air intake to see if it will pop and run at least a little. If so then the problem is most likely in the fuel system.

None of the above tests are conclusive, but that’s where usually begin b/c both are fairly easy to do and often provide major clues.

btw, given what you say I think you’d be better off to hire a pro to diagnose this for you. ask them if its ok if you watch while they explain what they are doing. the worst they can say is ‘no’. car repair is best learned from watching somebody who already knows how to do it.

Old gray haired mechanics who have virtually seen it all and know what the weak links are on most vehicles that they see don’t feel at all timid about pealing back covers and removing breathers and they have most everything that makes diagnosis convenient @George_San_Jose1. The learning curve for a beginning DIYer is very steep.