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Or, it may be something obvious to y’all. Bear with me, I’m just starting to work on my own trucks for the most part. I have some mechanical knowledge but certainly am no master mechanic. Anyway, this is related to the 1984 F150 I posted about a few days ago. Other than my small upgrades, it’s a stock 351w HO engine. It hasn’t run for probably 20 years. I’ve put on a new 1406 edelbrock carb, new spark plugs and plug wires, new starter and starter relay, today put on a new ignition control module (fender mounted duraspark II box), and a new ignition coil. Last year I put a new interstate battery in. New battery cables with two grounds, one on engine block and the other to the frame. So, after all that, here’s my problem. I’m still working on fuel, I’m pretty positive the mechanical fuel pump is bad. Put a little fresh gas in the carb. Twice now, this truck has fired and started after a couple seconds of strong cranking, and died the second I released the key back to the run position. Following this initial start, the engine cranks very slowly, and the battery voltage will have dropped to 12.3- 12.4 with key off. Both times the truck has started, the battery was fresh off the charger and fully charged. Usually holding around 13 volts after the fresh charge. Is this a bad battery, or something else? I understand there’s no steady flow of fuel to the carb, but both times I’ve put enough in the carb to at least idle it for probably 30 seconds. Any ideas?
Or, it may be something obvious to y’all. Bear with me, I’m just starting to work on my own trucks for the most part. I have some mechanical knowledge but certainly am no master mechanic. Anyway, this is related to the 1984 F150 I posted about a few days ago. Other than my small upgrades, it’s a stock 351w HO engine. It hasn’t run for probably 20 years. I’ve put on a new 1406 edelbrock carb, new spark plugs and plug wires, new starter and starter relay, today put on a new ignition control module (fender mounted duraspark II box), and a new ignition coil. Last year I put a new interstate battery in. New battery cables with two grounds, one on engine block and the other to the frame. So, after all that, here’s my problem. I’m still working on fuel, I’m pretty positive the mechanical fuel pump is bad. Put a little fresh gas in the carb. Twice now, this truck has fired and started after a couple seconds of strong cranking, and died the second I released the key back to the run position. Following this initial start, the engine cranks very slowly, and the battery voltage will have dropped to 12.3- 12.4 with key off. Both times the truck has started, the battery was fresh off the charger and fully charged. Usually holding around 13 volts after the fresh charge. Is this a bad battery, or something else? I understand there’s no steady flow of fuel to the carb, but both times I’ve put enough in the carb to at least idle it for probably 30 seconds. Any ideas?
When a battery is coming off a fresh charge the voltage will be initially as high as you read with the charger on. But it will steadily drop from there to your static charge. You'll be mostly there in a few hours after disconnecting. You'd like it to be around 12.6 or 12.7 after 2 or three hours. Leave it overnight and test it and see what you have. That'll give you an idea of true capacity.
12.3 to 12.4 would be about the minimum usable starting static voltage, prior to engaging the starter. You'd really like it a bit higher.
When a battery is coming off a fresh charge the voltage will be initially as high as you read with the charger on. But it will steadily drop from there to your static charge. You'll be mostly there in a few hours after disconnecting. You'd like it to be around 12.6 or 12.7 after 2 or three hours. Leave it overnight and test it and see what you have. That'll give you an idea of true capacity.
12.3 to 12.4 would be about the minimum usable starting static voltage, prior to engaging the starter. You'd really like it a bit higher.
Thank you for your quick reply. I agree with you, I’d like to see it at least 12.5. The fact that the engine cranks so sluggishly at that voltage concerns me; if the truck doesn’t start within about ten seconds, it begins to turn very slow and the interior lights dim down
Thank you for your quick reply. I agree with you, I’d like to see it at least 12.5. The fact that the engine cranks so sluggishly at that voltage concerns me; if the truck doesn’t start within about ten seconds, it begins to turn very slow and the interior lights dim down
Check your battery voltage right after that 10 second slow crank. If the static voltage has fallen off to a low value then the battery could be your problem. With a well tuned and fueled engine 12.3 to 12.4 will probably start it. But if you have tune up issues or a bad ground or starter or solenoid issues it's probably insufficient to overcome any of those weaknesses in your systems.
Thank you for your quick reply. I agree with you, I’d like to see it at least 12.5. The fact that the engine cranks so sluggishly at that voltage concerns me; if the truck doesn’t start within about ten seconds, it begins to turn very slow and the interior lights dim down
Up top in the How To there is a post on Voltage Drop Test.
Run that test and it will tell you what is making it turn over slowly.
Dave ----
Twice now, this truck has fired and started after a couple seconds of strong cranking, and died the second I released the key back to the run position. Following this initial start, the engine cranks very slowly, and the battery voltage will have dropped to 12.3- 12.4 with key off...
Most likely you've got two issues active at the same time. Different troubleshooting (and repair) for each fault. Don't just fix one, as it's possible to repair one fault and have it mask the other to some extent, making you think all is good.
1) Something is wrong with the starter system. For giggles, you could remove the carburetor or ignition coil so the engine has no possibility of actually starting. But regardless of whether the engine can actually run on its own, the starter system should be able to reliably get the crankshaft spinning at a good RPM. Seems like it works properly part of the time, but not consistently.
2) When the starter system does behave and gets the crankshaft spinning properly, it seems you've still got undiagnosed problems with the fuel and/or ignition system(s).
I'd concentrate on the starter system first. Note I said "system", not just the starter itself. This is a key distinction. Pour yourself some coffee and read up on a quick and simple test for the starter system:
The starter is the largest load your battery will see. The test verifies the battery's ability to supply the massive flow of electrons the starter needs. It also tests the ability of the rest of the system (cables, starter relay, and all connections) to deliver that massive flow without any undue restriction. If you can get the starter system to drag again, that's the best time to test.
You've already changed some parts in the starter system. Be aware one or more of your new parts could be bad. If you insist all those parts must be good because they are new, you will leave me with no choice. I will move into your guest room until you repent and realize the error of your ways. You will question your life choices that have brought you to this point. I will PM you a list of my dietary needs. Quiet time will be 7:00-9:30PM each each evening, as that is when I practice my tuba.
I've noticed you have listed battery voltage recorded at various times, but all unloaded (talking about the battery, not necessarily you). A voltage reading of an unloaded battery really doesn't mean much. In fact, it is very easy to misinterpret the value and condemn a good battery, or think a bad one is good. Because it's so easy to reach an invalid conclusion, I do not recommend putting much stock in such readings. A voltage reading with the battery under load? Now that's a different story, and one I highly recommend, as detailed in the test linked above.
Once you get the starter system working reliably, you can concentrate on why the engine won't actually start. That could be a fuel problem. Could be an ignition issue. Could be both. But get the starter system operating reliably first. That's a prerequisite for any engine. Then we can talk additional troubleshooting to figure out what's happening.
Karl, I'm glad you mentioned voltage under load. What voltage under load should the OP be looking for? It does require a helper or alligator clips on your tester though.
For the OP, Karl does a beautiful rendition of "Tequila" on the tuba, so you might want to clear the spare bedroom.
What voltage under load should the OP be looking for?
With the battery fully charged (very important!), 10.0V is the minimum you should see while the starter is engaged. Some sources say 9.5V is okay, but I prefer the higher limit. I know 10.0 sounds scary low for a 12V battery, but that is perfectly normal under the load of the starter.
Originally Posted by BigBlue2
It does require a helper or alligator clips on your tester though.
A digital meter with a min/max recording function is worth its weight in gold. You set up the meter and then turn the key. Then you push a button to see the minimum voltage recorded during the test.
Or you can position your meter to see it from the driver's seat. Another workaround is to disconnect the small wire from the S terminal on the starter relay. Set the parking brake and put the transmission in neutral (or park if auto). Momentarily connect a jumper from the battery's (+) terminal to the exposed terminal on the relay. This mimics the normal start command via the ignition switch. The starter relay will close and the starter will engage. Make sure to stay clear of the fan and belts, as the crankshaft will spin.
Originally Posted by BigBlue2
For the OP, Karl does a beautiful rendition of "Tequila" on the tuba, so you might want to clear the spare bedroom.
Thanks. In addition, you haven't lived until you've heard Muskrat Love on the tuba.
Back with an update. First, huge thanks to all of you for the tremendous amount of info and help. I replaced the fuel pump and swapped in my old battery for a new one as I’m pretty convinced it had gone bad. Primed the carb with a line running into a gas can, fired her right up. Running good, just need to fine tune the carb. Again, thanks to everybody. Now on to the brakes and A/C.
Brakes, I'd suggest you flush the old brake fluid using a power bleeder. I got mine from Summit racing. You can get qt's of DOT3 from most discount stores for about $7.00
Napa is a good place to get your brake parts from, they have been around forever and will be. You can get easy to bend brake lines there too for little money.
Brakes, I'd suggest you flush the old brake fluid using a power bleeder. I got mine from Summit racing. You can get qt's of DOT3 from most discount stores for about $7.00
Napa is a good place to get your brake parts from, they have been around forever and will be. You can get easy to bend brake lines there too for little money.
The power bleeder is a good idea, I’ll have to get one. As of now I have zero brake pressure, pedal collapses all the way to the floor when pressed. No brake fluid in the master cylinder. I’m sure there’s a leak somewhere, probably going to have to replace all the lines and vacuum hoses, and probably a new booster and master cylinder. As for the A/C, it doesn’t work at all, no air flow, nothing. On any setting. Fuse is good, popped a new one in it. Still nothing. When I get time I’m going to chase the wiring to see if there’s a fault somewhere.
Again, NAPA, will have all the brake parts you need. Most of us have replaced the master and booster. Hopefully by now, you can get good parts the first time. Some of us have been through a few MC or boosters to get a good one. Make sure you bench bleed the MC before install.
Make sure you can break the bleeder screws loose before you replace the shoes/pads, and find out the bleeder snaps off.
Oh, another thing about NAPA, they can get replacement parts in a couple of hours, once they even delivered the third right front caliper to my house one day.
My NAPA is a 2 mile drive and the only auto parts store in town. The other stores are about a 5-6 mile drive.
In the over twn years I've been going to NAPA, its common to see the same guys working there. it's nice to see the same faces.
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