Fuel pump

[oldmemberl68]

Can any one help
My mechanical fuel pump stops working when the engine gets hot around 210f by the dash temp gauge !
Leave it for 15/20 min and she will work ok !
I am thinking of fitting an electric fuel pump posable a facit one ??
Question could i fit it next to the fuel tank ! Leaving the mechanical still plumbed in
Ie the electrical one pushing through the mechanical one !
What electrical pump should i use
Any help or advice would be appricated
C3 427 400 auto

 

[Roscobbc]

Just go with a new replacement mechanical pump.......ethanol rots out the diaphragm

 

[Oneball]

A Facet pump might not deliver enough fuel for your engine. If you don’t want the standard pump you can get aftermarket mechanical ones or if you want electric look at American brands.

I have my doubts that the pump itself is the cause of your problem. I think it’s more likely to be that heat is causing a vapour lock in your system.

 

[Roscobbc]

Being a 400 hp engine - presumably its a tri-power and a 'early' C3...........fuel pump options are quite plentiful......however if you are keeping the car 100% stock you may struggle to find an uprated mechanical pump with the fuel inlet and outlet in the same position as stock.

 

[oldmemberl68]

Thank you for help and advice
yes its an L68 tri carb built in 68 reg 69
Im trying to keep it looking original as i can
I would like to put a replacment A C mechanical pump back on it but can not locate one at a sensable price.

Vapour lock !!!!! Oneball
How do i cure that .
At 210f there is no fuel coming out of the fuel pump if i remove the pipe up to the carbs !
Once again thank you for all your help

 

[Roscobbc]

Does it have a fuel return back to tank?

 

[teamzr1]

There are several fuel pumps from $25 to $55 US on Amazon

68 pump

Another one

Amazon search

 

[Oneball]

Vapour lock is the petrol in the pipes and pump getting hot and turning to vapour, which the diaphragm can’t pump. So to cure you can insulate the pimps and pump with some sort of heat shield or blanket. If you’ve got a return line like Rosco said making sure that is working helps too as it maintains a flow of fuel rather than it just sitting in the pipe getting hot.

Maybe it’s a combination of things the petrol getting hot and your pump isn’t working great so struggles to overcome any vapour in the lines.

Googling says the GM part number for your pump is 6416741 and putting that into the search in Rock Auto they have them. RockAuto

 

[oldmemberl68]

Thanks guys
No Rosco no return pipe !
solid pipe from pump to the carbs .
Thanks one ball
the pipes from the pump back are shielded
Im going to shield the pipes from the pump up to the carbs ?
The pumps on the market are not A C ! But replacement / carter ones ??? I may have to go with it for now
Yes i think you are right i think the problem could be a weak pump and vaporising fuel
I was hoping you was going to have some magical cue for vaporised fuel pipes ??
I give Rock Autos a call
Thank you teamzr1
Ill have a look
Thanks again for your help

 

[Roscobbc]

GM did some odd things with early C3's, and yes some C3's do not have a return line. I can understand that perhaps on a lo-po small block but certainly not a big block. BB's are known for hot running and associated percolation. The return line helps reduce the fuel feed temperature......although on a long hot journey as the tank gradually heats up the effects will be minimal. I had all these issues with my L36 390 hp at first.
Firstly replace the fuel pump (if only as preventative maintenance). IMHO 210 degrees is far too hot for normal running on an earlier C3 (and as happened to mine) will create percolation issues. Cures :- check out water pump. If original with a steel impeller look for cavitation erosion caused by historic use without anto-freeze. If in doubt renew with hi-volume replacement. Check that upper and lower rad hoses are ok and that the spring inside is ok. Check out radiator. Mine was shot so replaced it with a OEM pattern De Witt alluminium (kin' expensive though) Do make sure that viscous fan coupling is functional. Do make sure all foam and rubber sealing fillets inside the engine bay area in place. Do conside Redline Water Wetter additive......it really can reduce water temperature by a few degrees. Do source some of that heat reflective insulation stuff and wrap the fuel pipes close to the fuel lines. Mine runs at about 175 on mild days. Will get up to 185 on hot days in traffic and even 190 if held up. If will run 'wooly' off idle at these higher temperatures AND I do have hot restart issues......but that's a starter motor issue. Have you checked the timing? If it's too retarded it can run hotter.

 

[oldmemberl68]

Thanks Rosco
Thank you for the feed back
I have owned the car for 35 years
This is a new problem never had issure with her before
Water pump is original
Hose's are new / spring intact
Always kept 50% antifreeze
Rad looks ok ..
I will give it a flush through
Viscous fan hub ok
Seals ok
I will get the wetter water
I will insulate pipes
Timing is 4 ° btc to stop her pinkin !
She normally runs at 180 ish
Just noticed that when she cuts out the gauge was reading 200/210f
So my problem lies with running hot !!!!! Basically
May be fitting electric fans could also help ?
Ive just put a high torque starter motor ( wasp ) on as i was fed up with getting the standard one overhauled (5 times ) now she turns over nice and quick with no fuss .
Few jobs to sort out over the next few weekends
Thank you Rosco

 

[Roscobbc]

Thanks Rosco
Thank you for the feed back
I have owned the car for 35 years
This is a new problem never had issure with her before
Water pump is original
Hose's are new / spring intact
Always kept 50% antifreeze
Rad looks ok ..
I will give it a flush through
Viscous fan hub ok
Seals ok
I will get the wetter water
I will insulate pipes
Timing is 4 ° btc to stop her pinkin !
She normally runs at 180 ish
Just noticed that when she cuts out the gauge was reading 200/210f
So my problem lies with running hot !!!!! Basically
May be fitting electric fans could also help ?
Ive just put a high torque starter motor ( wasp ) on as i was fed up with getting the standard one overhauled (5 times ) now she turns over nice and quick with no fuss .
Few jobs to sort out over the next few weekends
Thank you Rosco

Timing is very low at 4 degrees - having said that - timing is set at idle so the rate at which the advance curve changes and total timing will have more of an effect on any overheating than just at idle. Be interesting to know what total advance is. BB engines are not known for ignition related pinking. My original L36 427 is same spec as yours other carbs and would run at high degrees of advance without pinking! - Have you tried using V Power or Esso 99?. Stock viscous fan, radiator and shroud are really as good as it gets for a C3 - electric fans are not as effective (many others will disagree) - I removed the front number plate from it stock position - it covers the centre grille - blocks air flow in to the front nacelle area - see below how much is blocked - I made some brackets and dropped the number plate down about 8/10 inches and reduced running temperture several degrees this really helped to keep nearly 600 bhp from boiling-up.
You'll notice how outer grilles will not allow much cooling air to pass (even if plastic headlamp blinds blow back under wind pressure the headlamps are still partially blocking airflow. Most of the cooling air comes from the slots lower dow.n in the nose cone

 

[Oneball]

I would double check your viscous fan. Just because it seems to be spinning quickly doesn’t mean it’s working.
Cold and engine off there should be quite a lot of resistance to turning it by hand. Cold and a few minutes running and you should be able to noticeably slow it with a rolled up newspaper. Hot and running a rolled up newspaper shouldn’t do anything.

Ive got an electric fan on mine but only because it’s a race car. Like Rosco I think the viscous fan and shroud is the best set up.

 

[Roscobbc]

I would double check your viscous fan. Just because it seems to be spinning quickly doesn’t mean it’s working.
Cold and engine off there should be quite a lot of resistance to turning it by hand. Cold and a few minutes running and you should be able to noticeably slow it with a rolled up newspaper. Hot and running a rolled up newspaper shouldn’t do anything.

Ive got an electric fan on mine but only because it’s a race car. Like Rosco I think the viscous fan and shroud is the best set up.

Viscous fan couplings are like PCV valves - they might all look alike but are definately not all the same (depending of year of vehicle and engine spec's.) They also differ significantly in price and availability, expecially for a genuine OEM replacement. The 'clue' (in addition to Oneballs suggestion) is to carefully observe where the alloy viscous hub rotates on the shaft (that mounts to the water pump extension)...........evidence of moisture or a build-up of crud where the silicon fluid within the hub has leaked past the shaft seal generally means that the unit is shot and needs replacing.

 

[oldmemberl68]

Thanks Rosco
I only use v power or premien fuel
I will look into the timing and see if that helps
i set the timing at 4 ° a good few years back and never had any running problems just pinking !
At the standard setting 12° i seem to remember
Ill move my number plate as well
My number plate is a full size one
Headlight shields are removed already !
Thanks oneball
I will check the fan hub
I can hear the fan cut in after about 15 min running and driving along the road you can hear the fan note change its quite noticeable
Thanks again guys
On the to do list
Rad flush.Water wetter. heat fabric shield. Timing.number plate.rad shroud sponges/seals . And Possibly a fuel pump
Ill get a look at it over the next few weekends
Thanks you for all the help and advice

 

[Forrest Gump]

Might be worth checking the thermostat. Something appears to have changed to cause your hotter running, perhaps thermostat isn‘t opening fully.

 

[Roscobbc]

Problem with a 50 y/o car is that you can't be sure of previous owners maintenance regimes. Flushing out rad alone may not be enough to dislodge any compacted crud in the blocks water galleries........and then, when you do an effective flush you run a risk of leaks from rad and even worse core plugs.......

 

[oldmemberl68]

Thanks
Forrest Gump
Will do as matter of course
Thanks
Rosco that true over the years ive had the car i have changed the coolant a number of times and flushed it through always replenishing with 50% blue anti freeze
This time taking your advice and adding water wetter

 

[Corvette]

“I have owned the car for 35 years”. Respect!

 

[Roscobbc]

I didn't start off from a level playing field with mine - and whilst the current cooling system is coping reasonably well with cooling 8 litres and close on 600 HP its really no different cooling a 396, 427 or 454 cu in.
In truth it was my 427 engine that gave me issues re. cooling initially - most of what I did to that payed dividends when the new engine went in.......the only addition 'after' the new engine was fitted was the new radiator - the original had deteriorated badly and was leaking all over the place.
One of the first things when getting the car was to replace the stock exhaust system with Hedman headers, 2 1/2" pipes and low restriction mufflers #1. Surprisingly this helped the engine run cooler and fuel pipe evaporation was minimised. The OEM water pump has a steel impellor - this was eroded due to lack of coolant and cavitation damage. Replaced with high volume ally aftermarket unit - an improvement #2. I changed the timing curve - used an 'over the counter' set of distributor bob weights and springs #3. As previously noted - dropped front number plate down 6/8" form better airflow #4. Used Water Wetter #5. Made sure ALL oem radiator to front rad mount/hood rubber/foam closure seals were in place #6. Fabricated a suplimentary shroud lower extension from corrogated plastic sheet, sealing it with Sikaflex #7. New OEM style DeWitt alluminium radiator #8. 15 or 16lb pressure cap #9
There is no one secret to keeping the engine cool - just multiple small ones. All of the # numbered mods above only dropped the temperature down perhaps by 1 or 2 degrees each, individually not making too much difference - however as a group of improvements they reduced summer temperature by 10 or 12 degrees. In fact during winter the engine can struggle to creep over 150 degrees on shorter low speed journeys. I don't bother with Water Wetter any more (don't need to) but that was honestly good for a couple of degrees. Its still a hot place to be - and the engine eminated lots of heat - but doesn't overheat as such.