Engine bogging / possible fuel boiling

[MikeJones]

I’ve had this car for just a few months and still learning its quirks. What I’ve been running into is while just cruising any speed the engine runs perfectly, but if I decide to get in the pedal it at any speed it will stutter and bog down. Originally, since it doesn’t like sudden jump in rpm, I was going to try a new ignition coil but what I have also noticed is that the prior owner ran the fuel line almost on top of the intake and under and around the heater hoses, I suspect this is causing the fuel line to soak up a lot of heat and cause the fuel to boil.

No problems starting when cold, only after it’s been warmed up. It will stall occasionally at lights or when parking which has me now thinking it’s an issue with the routing of the fuel line or possibly something else. Here’s a picture of the fuel line as it is now. Any advice is appreciated. Thanks

 

[giantpune]

I have my fuel lines run like that on more than a few carb'd engines. No boiling or stuttering issues.

Edelbrock and summit both sell that same style fuel inlet that goes down, under the choke, and then along the intake. Presumably thousands of people out there are using them.

On another note, how many HP does the steel braided vacuum lines add?

 

[Steve McMahan]

Wondering, have you noticed if you can “get in the pedal“ when the engine is cold? If the only time you have this issue is a up to temp motor, it could be the coil, as you suspect. If you have the same issue before getting to operating temp, I would suspect a fuel flow issue.

 

[MikeJones]

I have my fuel lines run like that on more than a few carb'd engines. No boiling or stuttering issues.

Edelbrock and summit both sell that same style fuel inlet that goes down, under the choke, and then along the intake. Presumably thousands of people out there are using them.

On another note, how many HP does the steel braided vacuum lines add?

Thanks for the reply and laugh. The prior owner installed the braid on almost every hose and I hadn’t gotten to removing it yet. Waiting for a day where I feel like getting my hands tore up with the frayed ends.

I did see where Edlebrock offered this style inlet and can possibly rule this out as an issue.

 

[MikeJones]

Wondering, have you noticed if you can “get in the pedal“ when the engine is cold? If the only time you have this issue is a up to temp motor, it could be the coil, as you suspect. If you have the same issue before getting to operating temp, I would suspect a fuel flow issue.

I hadn’t considered a flow issue. I have noticed the same issue before it’s gotten to temp. I appreciate the reply and will start digging into the fuel filter and pump. Probably throw a gauge on it tomorrow and see if it may be the pump.

 

[Paul M]

I’ve had this car for just a few months and still learning its quirks. What I’ve been running into is while just cruising any speed the engine runs perfectly, but if I decide to get in the pedal it at any speed it will stutter and bog down. Originally, since it doesn’t like sudden jump in rpm, I was going to try a new ignition coil but what I have also noticed is that the prior owner ran the fuel line almost on top of the intake and under and around the heater hoses, I suspect this is causing the fuel line to soak up a lot of heat and cause the fuel to boil.

No problems starting when cold, only after it’s been warmed up. It will stall occasionally at lights or when parking which has me now thinking it’s an issue with the routing of the fuel line or possibly something else. Here’s a picture of the fuel line as it is now. Any advice is appreciated. Thanks

I had a similar problem earlier this summer. Yes, my fuel was vapor locking. It acted as if it was running out of gas, which it actually was. It happened on a couple of hot days in a row after getting the motor hot. This simple little set up stopped it completely. Of course, I couldn't see it with the air-condition compressor in the way. I removed it temporarily, since it will involve a bit of investment and I'd rather put the money in a True track posi w/ some gears. I'm still waiting on that since, I may have to swap to 31 spline axles along with it. Your fuel line seems to be riding on the radiator hose. You need a lil separation along with an aluminum shield between it. Even if you just wrap a strip around the hose for a couple of inches.

 

[Sheriff41]

Nice fab work there @Paul M

 

[Paul M]

Nice fab work there @Paul M

Ha ... that little aluminum pc was just aviator snips. It was harder to cut the slice down the pc of rubber hose to use as edge guards. I did make a bracket to hold the power steering cooler up where it used to be mounted on the ac compressor. Apparently, they make 2 different types of coolers, one that mounts lower and one that mounts on the AC compressor. They wanted too much $ for the other type so I just mounted this one (for the time being) The car came with AC, so I'll eventually put it all back in.

 

[Sheriff41]

Ha ... that little aluminum pc was just aviator snips. It was harder to cut the slice down the pc of rubber hose to use as edge guards. I did make a bracket to hold the power steering cooler up where it used to be mounted on the ac compressor. Apparently, they make 2 different types of coolers, one that mounts lower and one that mounts on the AC compressor. They wanted too much $ for the other type so I just mounted this one (for the time being) The car came with AC, so I'll eventually put it all back in.

Yep. Having the vision and being able to engineer fab work are usually the more difficult steps in creating solutions.

 

[MikeJones]

@Paul M -
Great job on the aluminum heat shield. I will see if I can make something to give it some space. Thanks for the suggestion

@giantpune - all the braided stainless is gone and did locate a coolant leak I had been chasing. The prior owner must of used a roll of electrical tape to keep the ends from fraying and cinched down with gear clamps. Getting to the clamps on the tstat housing were a pain the way he had them installed.

 

[MikeJones]

I dug into the fuel line this morning and it was running almost right on top of the intake and crossed over two heater hoses. I adjusted the inlet fitting at the carb to slightly lift off the intake and added a fuel filter and pressure gauge. I also slightly reformed the hard line to get it off the heater hoses. The pressure gauge reads around 2.5psi and I believe this carb needs to be around 5.5 - 6.5 per Edlebrock spec. The fuel pump is probably original to the car and fortunately when I changed the oil I didn’t see or smell gas in it but will be changing the mechanical fuel pump as a precaution. Is there anything else I should be looking at as a possible issue? The hard pipe looks good and I’m not seeing any kinks or fuel leaks anywhere

 

[Steve McMahan]

I think I would wait to make more changes unit the pump is replaced. One change at a time is best.

 

[MikeJones]

I think I would wait to make more changes unit the pump is replaced. One change at a time is best.

Thanks Steve. Hoping it’s just the fuel pump and I’ll report back any changes good or bad.

 

[giantpune]

I think I would wait to make more changes unit the pump is replaced. One change at a time is best.

In general, I agree with this. I would make an exception for some cases like if you were already planning to replace the line from the pump to the carb, or the new pump had different outlet thread pattern than the old pump.

In those cases, it just makes it more work to replace the pump and connect it to the old line, then turn around and disconnect the old line to put in the new line. Just replace the pump and the line. If the problem is fixed, who really cares if it was the old pump or line that caused it?

 

[Paul M]

I dug into the fuel line this morning and it was running almost right on top of the intake and crossed over two heater hoses. I adjusted the inlet fitting at the carb to slightly lift off the intake and added a fuel filter and pressure gauge. I also slightly reformed the hard line to get it off the heater hoses. The pressure gauge reads around 2.5psi and I believe this carb needs to be around 5.5 - 6.5 per Edlebrock spec. The fuel pump is probably original to the car and fortunately when I changed the oil I didn’t see or smell gas in it but will be changing the mechanical fuel pump as a precaution. Is there anything else I should be looking at as a possible issue? The hard pipe looks good and I’m not seeing any kinks or fuel leaks anywhere

I honestly don't see how it could not vapor lock like that on a hot motor in the summer. Have you tried it since you adjusted the line off the intake and water hose. Also, the only carbs that function on 2 1/2 psi are prehistoric Strombergs and Holley 94's. Yes @ 6 psi. at7+ that carb won't function properly.

 

[MikeJones]

I honestly don't see how it could not vapor lock like that on a hot motor in the summer. Have you tried it since you adjusted the line off the intake and water hose. Also, the only carbs that function on 2 1/2 psi are prehistoric Strombergs and Holley 94's. Yes @ 6 psi. at7+ that carb won't function properly.

I did take it for a ride after making the adjustments but didn’t have any improvements. I’m going to replace the fuel pump and any rubber fuel line at the tank area. The hard line going from the pump to carb seems good but as a precaution may replace as @giantpune suggested. I’ll also check the entire line coming from the tank.

I saw in another thread the recommendation to use a Carter M4009 with the integrated filter from the 65 Mustang but Carters website doesn’t show it as compatible, so may go with original factory style.

 

[MikeJones]

In general, I agree with this. I would make an exception for some cases like if you were already planning to replace the line from the pump to the carb, or the new pump had different outlet thread pattern than the old pump.

In those cases, it just makes it more work to replace the pump and connect it to the old line, then turn around and disconnect the old line to put in the new line. Just replace the pump and the line. If the problem is fixed, who really cares if it was the old pump or line that caused it?

I think the line is good but considering this also. Rather do it once versus having to go back and possibly have to do it again.

 

[giantpune]

I saw in another thread the recommendation to use a Carter M4009 with the integrated filter from the 65 Mustang but Carters website doesn’t show it as compatible, so may go with original factory style.

If you want a filter, i typically use one that screws directly into that fuel itlet line that you already have.

On one car, i used a preformed metal line from the carb up to that area, then a crush sleve to a -6an fitting. That connects to the filter and then to the 90 degree fuel inles you already have. It looks pretty tidy.

On some other cars, i just ran a rubber hose to a barb, similar to your current setup. But there's a little -6an filter stuck in right before the inlet.

 

[73inNH]

Reads like a tuning issue to me. Like accelerator pump is clogged or too small.

 

[MikeJones]

Reads like a tuning issue to me. Like accelerator pump is clogged or too small.

Fuel pressure seems very low which has me thinking part or all of the problem is with the fuel pump but I will check the accelerator pump first since that’s fast and easy. Thanks