Hello all,

The other week I posted a question about a faulty terminal connector when I was troubleshooting an issue with my 1980 L48. A new connector was crimped on but the original problem is still present which is a hard start when the engine is hot.

I wanted to start a new thread covering all things that have been done and tested and where I am with the car now.

First the problem. When the car is cold it starts fine, no issues. If I run around town for a few minutes, park the car, shut it off and turn it back on in a couple of minutes it sounds like I have a dying battery. For the most part the car has always started but it sounds like it doesn't want to start when hot. This is not a vapor lock problem.

Now let me explain what change I think caused the issue. I replaced the stock exhaust manifold with a set of ceramic coated headers and side pipes. Shortly after I made this change the problem slowly started to happen to the point where it happens every time I try to start the car when hot. It also feels like it might be getting worse but that could be in my head. Also for reference the car is a 1980, L48 with an auto transmission. Besides the side pipes and headers, the only other modification to the engine is a newer Edelbrock manifold installed before I bought the car a few years ago.

What I've done so far: I've replaced the battery with a new 1000 CCA battery, this was tested and in good order. I have replaced the starter 3 times, right now I have a Powermaster Powermax in there, again, this has tested good. I have tried a DEI starter wrap with no luck. I have also replaced both the negative and positive battery cables. I have added a separate ground from the negative battery bolt on the chassis directly to the starter case. The timing is correct and set to around 12 degrees which if I retard anymore I bog down. I have just replaced the engine harness that connects to the starter and ties into the connector under the wiper motor.

None of these changes have made any effect on the hard starting issue. However I think I have narrowed down the cause of the hard start, I just haven't figured out the culprit. When the engine is cold the voltage at the battery will drop from 14VDC to 10VDC when you start the car. But when hot it goes from 14VDC down to 7VDC. So to me this sounds like the starter is pulling more current when the engine is hot then cold but why so much more? Before I start diving into this tomorrow, what should I check, test and look for? Some people have mentioned that I should check/replace the alternator wire from the battery box to the alternator, but I'm not sure how this ties into the problem. However, I'll try it tomorrow as a step to correct the issue.

Thank you,
Sam

 

HMM.For your L48..Try advanceing the timing up to 12 degrees above TDC..How's the carburetor/Good, rebuilt..original flat? You have any parasitic current draw/?Jim

 

AS anote, properly adjusted carb on warm engine..usually no need for any gas pedal action..SHOULD fire back up with the turn of the key..

 

Hi Jim,

I can try to advance the timing, that's not a problem. It actually sounds better that way but several people have told me that is part of the problem and retarding the time is correct but I will try this.

The carb is a recently rebuilt Quadrajet, I had it completely gone over last summer and it works great.

I'm guessing you're asking if I have a drain on the electrical system? Not that I'm aware of, nothing on the electrical side has changed. If you mean something else, any details would be great and I'll do my best to answer.

Thanks,
Sam

 

Lets see...if I read correctly, everything was swapped except the main positive battery cable? Its possible its corroded on the inside, or has a bad crimp terminal.

Did you clean/replace chassis ground bolt at neg bat cable?

Check your main cables this way. Get your DMM set to DC volts. Put the probes across both ends of the cable. May need to extend with wire. Then crank the engine, watch for voltage drop on the meter. Should be like a volt or so, and compare both hot and cold. If more suspect a problem.

 

Hi Mike,

Actually the main positive battery cable was also replaced.

Yes, I cleaned the chassis ground bolt and ran a seperate 4AWG cable from that bolt directly to the starter housing bolt. (Where the starter bolts to the block)

 

Sam.NO REASON FOR HARD CRANKING ON HOT engine..other than electrical, fuel..cooling system..sounds like you've attended to the most obvious things already.When the Roch QJet was rebuilt..was the float upgraded..often the old factory floats get loggy and unresponsive..
DO try advanceing the timing..Fact timing was not for optimal anything..Jim

 

Yes, new upgraded floats in the carb.

I will do that with the timing tomorrow and see how it goes, thanks!

 

Do the timing changes a few degrees at a time and don't neglect the twin idle adj screws and fuel mix..as you tweak the carb-timing..
Jim

 

It sounds like the starter is on its way out .

 

As I recall the OP has replaced and even upgraded the starter...Jim

 

samdjr74,

When you turn your key to the start position, did you ever check what the voltage is at the solenoid connection for that wire? (engine hot).

 

No..Never had the need for that check arise..Couldn't tell you what such a reading-test should show all things being right..Jim

 

Basic troubleshooting for voltage thru the ignition column switch to the solenoid. The OP has stated that he replaced the starter harness and there was no change. He also stated that his battery voltage drops to 7 volts when cranking hot. There has to be a resistance problem somewhere in the system.

 

I'll take a look at the timing tomorrow. One thing to mention is once it's started and even hot it runs fine so wouldn't this rule out the carb?

 

3Rd starter, and now I'm running a high torque mini unit.

 

Correct

 

Not yet but I'll do that tomorrow. Should I be checking the red or purple wire?

 

The 'purple'.

 

Thanks, I'll set up 2 tests tomorrow morning , first I'll measure the purple wire when starting cold and second the same thing starting hot.