fuel pump going bad?

[magg383]

I think my 3 yr old Precision fuel pump that's on my 1969 383 in my 73 Challenger is pumping out too much pressure/gas and in return, flooding my carb, along with some of my spark plugs. I had plugs last yr that fouled once, but this yr it has gotten worse. The worse plugs are generally on the passenger side, 4,6,8 and sometimes plug #7 on driver's side, probably cause of engine tilt. When I take these plugs out, they are either wet or have sticky glossy black stains on them. I'm running NGK XR4 plugs, gapped at .035 and I'm currently on the second set this yr. After cleaning the plugs or replacing them, it runs good for a trip or two.
The 2 main symptoms while on the road are:
1) slight hesitation, especially in 1st and 2nd gear
2) backfiring in the exhaust pipes while deacceleration in 3rd gear

I thought that it was the old Edlbrock 750 carb initially, so I took the air horn off and noticed some crud in the bowls along w 2 incorrect jets, along w the wrong metering rods which weren't even the same as ea other. Floats were set correctly. Unfortunately, after correcting these issues, it was having the same issues.
I decided just to upgrade to a new AVS2 650 #1906 carb. I also purchased a 1" Mr. Gasket plastic type spacer to help w vapor lock. (I mounted it w the cavities mounted on the intake manifold side) I also put a new fuel filter on.
Unfortunately, after the new carb along w a new set of plugs, it was doing the same thing after running well for the first few miles, but after turning the motor off for about 15 minutes, on the way home it started to act up again.
Yesterday was the worse day yet. After cleaning the plugs, on the road it was hesitating and backfiring again but this time, it stalled while going around a street corner and really struggled to restart. Once it did restart, it barely stayed running to get me home w some pinging also and while going up my steep driveway, the motor pinged worse yet. This was something new.

I suspect now that it is a bad fuel pump and plan on purchasing a Carter M4589 pump along w a new fuel filter. I have heard that Carter pumps are a lot better quality vs Precision.
I'm sure this has nothing to do w my fuel related symptoms but just to note, after replacing my old Chrysler distributor 3 months ago w a new Proform #440-431 distributor is when the issues seemed to of gotten worse.

Any suggestions appreciated!

 

[DetMatt1]

this sounds like an ignition problem to me.

 

[Challenger RTA]

backfiring in the exhaust pipes while deacceleration in 3rd gear

In short the voltage regulator is going bad or bad connection . Don't forget about the ground. Alternator? The coil is not getting the correct voltage.
Way back when there was a mechanical voltage regulator it was more common. I experienced it just a few times. The tattle tail was the back firing when shifting gears.

 

[magg383]

I think my 3 yr old Precision fuel pump that's on my 1969 383 in my 73 Challenger is pumping out too much pressure/gas and in return, flooding my carb, along with some of my spark plugs. I had plugs last yr that fouled once, but this yr it has gotten worse. The worse plugs are generally on the passenger side, 4,6,8 and sometimes plug #7 on driver's side, probably cause of engine tilt. When I take these plugs out, they are either wet or have sticky glossy black stains on them. I'm running NGK XR4 plugs, gapped at .035 and I'm currently on the second set this yr. After cleaning the plugs or replacing them, it runs good for a trip or two.
The 2 main symptoms while on the road are:
1) slight hesitation, especially in 1st and 2nd gear
2) backfiring in the exhaust pipes while deacceleration in 3rd gear

I thought that it was the old Edlbrock 750 carb initially, so I took the air horn off and noticed some crud in the bowls along w 2 incorrect jets, along w the wrong metering rods which weren't even the same as ea other. Floats were set correctly. Unfortunately, after correcting these issues, it was having the same issues.
I decided just to upgrade to a new AVS2 650 #1906 carb. I also purchased a 1" Mr. Gasket plastic type spacer to help w vapor lock. (I mounted it w the cavities mounted on the intake manifold side) I also put a new fuel filter on.
Unfortunately, after the new carb along w a new set of plugs, it was doing the same thing after running well for the first few miles, but after turning the motor off for about 15 minutes, on the way home it started to act up again.
Yesterday was the worse day yet. After cleaning the plugs, on the road it was hesitating and backfiring again but this time, it stalled while going around a street corner and really struggled to restart. Once it did restart, it barely stayed running to get me home w some pinging also and while going up my steep driveway, the motor pinged worse yet. This was something new.

I suspect now that it is a bad fuel pump and plan on purchasing a Carter M4589 pump along w a new fuel filter. I have heard that Carter pumps are a lot better quality vs Precision.
I'm sure this has nothing to do w my fuel related symptoms but just to note, after replacing my old Chrysler distributor 3 months ago w a new Proform #440-431 distributor is when the issues seemed to of gotten worse.

Any suggestions appreciated!

I just thought of an additional suggestion related possibility. This spring I replaced my old smaller main engine braided ground strap w a thicker/wider braided strap. The blue electronic ign. box and the chrome voltage regulator share the same hole on the firewall. Just to note, paint is scraped off that firewall bolt area. I just now noticed that I put the voltage regulator mount end under the EIC box mount end and noticed now that there is an angled gap under the EIC box on the firewall.

If this isn't creating a flush mount on the firewall and not creating a good electronic ground, can it cause the voltage going to the coil to drop and in return struggles to ignite the fuel causing my spark plug issues resulting in my hesitation and deceleration backfire




UPDATE ON ABOVE MESSAGE:
I exchanged it to where now the EIC box end is now flat on the firewall vs the voltage regulator. There is still a small gap, not as wide as before though.
ALSO, I noticed that when I attached the braided strap 3 months ago to one of the top intake manifold bolts, I put a regular washer under the bolt, then the strap end, then placed a star washer between the strap end and directly on the manifold side.
Could of this set up also have created a possible hidden grounding bottleneck issue similar to the set up as above, but this time by having 2 washers in 2 different locations on that bolt?

Also, doesn't a weak spark just cause lean misfire and not rich flooding (wet plugs= too much fuel) like in my case?

2nd UPDATE:
I corrected both sides of the ground strap.
Checked Coil voltage w key on, (engine not running) w voltmeter on red on + terminal and blk lead on intake manifold ground.
I'm ONLY getting 2.9 volts! I understand 9-10 is normal?
Battery is good, reading at 12.63 volts

Checked Ballast resister input voltage w key on (engine off) w + meter on input side from ign., blue wires and blk lead on manifold ground.
I ONLY get a fluctuating 10.4-10.5 volts! I understand 12-12.6 is normal?

What do these 2 low readings point to w the way my engine has been running this yr?

 

[pschlosser]

I can think of six or seven things that may cause the behavior you describe. And you may get varying advice from this community. But I will say this, begin the process to eliminate things. Once you test, resolve and confirm one issue, cross that off your list, and you won't need to return to it, or keep guessing.

I concur with Challenger RTA, this seems likely an ignition or electrical issue. I would begin with confirming the voltage regulator is well grounded to the chassis AND engine. Since you changed carbs, and still see pretty much the same problem(s) I don't think the issue is the carb. Fuel (pump) delivery is easy to spot, if the the levels in the float bowls are lower than they're supposed to be. So start with the ignition, and cross that off the list of possibilities.

 

[heminut]

I'm going with ignition issues too. Before I got even halfway through your first post I was thinking ignition, not fuel. The fact that the issue persisted after putting a new carb on the car pretty much confirmed it for me.

 

[magg383]

In short the voltage regulator is going bad or bad connection . Don't forget about the ground. Alternator? The coil is not getting the correct voltage.
Way back when there was a mechanical voltage regulator it was more common. I experienced it just a few times. The tattle tail was the back firing when shifting gears.

Yesterday I performed an IGN-RUN voltage drop test. I got 11.4V at the blue wire ign. switch (molex) on both sides and 10.66V at the ballast input side (blue wire). A 0.74V drop

The day before, same test, I got a 0.54V drop.
Now today, I just got a low 0.27V drop!!
Do you think these are acceptable #'s and is it normal to have day to day differences?
I read somewhere that under .30V is excellent, .31-.60 is very good, .61-.80 is acceptable

Also, 2 days ago, I rerouted my battery neg. cable to an engine mount bracket from being attached to the painted P/S bracket that had 5 washers being used as a spacer to the water pump!! I'm sure this had to help out somewhat w voltage drops?

Other notes:
Coil Positive Voltage test was 3V w key on. (Only 3V because ECU grounds coil when engine not running)?
Coil Positive Voltage test w jumper from +battery w key off was 11.65


My battery voltage was at 12.16V w key in the on position

New engine wire harness 2 yrs ago
Repaired a couple electrical meltdown locations 3 yrs. ago, inc. main red and black wire bulkhead locations

 

[magg383]

Yesterday I performed an IGN-RUN voltage drop test. I got 11.4V at the blue wire ign. switch (molex) on both sides and 10.66V at the ballast input side (blue wire). A 0.74V drop

The day before, same test, I got a 0.54V drop.
Now today, I just got a low 0.27V drop!!
Do you think these are acceptable #'s and is it normal to have day to day differences?
I read somewhere that under .30V is excellent, .31-.60 is very good, .61-.80 is acceptable

Also, 2 days ago, I rerouted my battery neg. cable to an engine mount bracket from being attached to the painted P/S bracket that had 5 washers being used as a spacer to the water pump!! I'm sure repairing this terible connection has to help out w ANY type of a voltage drops?

Other notes:
Coil Positive Voltage test was 3V w key on. (Only 3V because ECU grounds coil when engine not running)?
Coil Positive Voltage test w jumper from +battery w key off was 11.65


My battery voltage was at 12.16V w key in the on position

New engine wire harness 2 yrs ago
Repaired a couple electrical meltdown locations 3 yrs. ago, inc. main red and black wire bulkhead locations

 

[Challenger RTA]

With the key in the off position. Should have at the alternator output post battery voltage.

The drop doesn't seem to bad. There are connections there that can loss a little at each one. I'm guessing your checking voltage with the motor not running. When the motor is running I would say you should see a higher voltage.
It adds up. Battery terminals both. Negative too and connections. Neg motor ground and chassis ground. Positive connections, fusible link, bulkhead connection in , molecular in, ign sw, molex out,bulkhead out then the resistor.

I'm going to post an other check.

 

[Challenger RTA]

Battery Hydrometer Readings Chart​

State of Charge	Specific Gravity Values for Temperate Climates	Specific Gravity Values for Tropical Climates
Fully Charged	1.250 – 1.280	1.210 – 1.230
75% Charged	1.220 – 1.240	1.190 – 1.210
50% Charged	1.190 – 1.210	1.160 – 1.180
25% Charged	1.160 – 1.180	1.130 – 1.150
Discharged	Below 1.160	Below 1.130

The one thing that is overlooked is: When the specific gravity reading differs 50 or more between cells the is a problem with the battery.

Also at 1.125 it's an anchor it's never coming back!

It will and still work for a while.

Factors Affecting Specific Gravity Readings​

Several factors can influence the specific gravity readings of a battery:

• Temperature Considerations: The specific gravity of a battery’s electrolyte can vary with temperature. In colder climates, the specific gravity might be slightly higher, while in hotter climates, it might be lower. Always consider the ambient temperature when interpreting readings.
• Electrolyte Strength in Extreme Climates: In extremely cold or hot climates, the strength of the electrolyte can be affected, leading to variations in specific gravity readings. It’s essential to be aware of these variations and adjust maintenance routines accordingly.
• Tips for Accurate Readings:
• Always ensure the hydrometer is clean and free from any residual electrolyte from previous readings.
• Take readings at a consistent time, preferably when the battery has been at rest.
• If unsure about a reading, it’s always a good idea to take a second or even third reading to confirm.

 

[Challenger RTA]

With the key in the on position. there will be voltage at the alternator output, it's going to be lower than what it was with the key off, because the entire vehicle is energized. The voltage drop is going to be more you can still you can see it go from
12.5 down to 11.7. Still going to have near battery voltage.

 

[Challenger RTA]

The magnetic pick up can cause starting issues and misfires. Be it's wore out or not getting the right voltage. I your not getting any where. Hot wire power to the run side of the resistor. It will start with the ignition switch. But it will keep running until you disconnect it from the battery.
The video below goes through a few.

 

[Avalanche]

I had avery similar issue. When the engine got warm it would stall and have a hard time starting. I thought it was vapor lock, but it turned out that when the distributor got hot, the magnetic pick up would loose power occasionally. I also had a proform distributor. I am in the process of installing a new firecore distributor to see if it cures the problem. Will let you know how it turns out.