Plymouth 40 Posted June 12, 2011 Report Posted June 12, 2011 Hello all , I have a question about the fuel consumption of a P9 engine, I am just driving the Plymouth P9 for a month now and it runs and drives very nice, I just been to Normandie in France with it but i was a little consurned about the fuel consumption . I did not get it beter than 8-9 miles a US gallon .. I read about 14 -17 miles a Gallon in this forum for similar engines. We do have overhere standard unleaded Ron 95 The vacuum advance is working, engine runs fine etc etc. Setting of the accelaration pump is on the summer position . Do i have to live with it or are there any improvements to make. Are there smaller nozzles for sale for the carburettor?? Like to here from you regards Paul Quote
Andydodge Posted June 13, 2011 Report Posted June 13, 2011 Paul, run it on standard or 95 BUT NEVER any fuel with Ethanol........ethanol will kill the rubber parts in the fuel lines,fuel pump etc. Usual tips are plugs/points/condenser/plug leads..........check the vaccum diaphram on the dissy, also what sort of air cleaner are you running?.........if an original oil bath cleaner, make sure its clean & un clogged up, also clean the filter in the cap on the oil filler tube beside the generator & distributor. Check the timing, should be approx 10degrees BTDC. Also US gallons are smaller than Imperial UK gallons.......recheck what you are using your calculations based on........lol.......and finally 1940 Plymouths are as aerodynamic as a brick shithouse(I know I have a 1940 Dodge & 1941 Plymouth brick shithouses).........always when taking fuel consumption figures make sure YOU are leaning forward in the car, are at YOUR minimium weight and you have a strong tailwind............lol.........btw welcome to the BEST forum for mopar 6's on the web........regards, from Australia..Andy Douglas Quote
Andydodge Posted June 13, 2011 Report Posted June 13, 2011 Paul, also check that the carby is in good condition, maybe put a kit or thru it or at least a new needle & seat and recheck the float level............andyd Quote
P-12 Tommy Posted June 13, 2011 Report Posted June 13, 2011 Welcome Paul and we would like to see pictures. Tom Quote
TodFitch Posted June 13, 2011 Report Posted June 13, 2011 Andydodge covered all the engine basics, so I'll just add: Dragging brakes? In any case something is not up to snuff as I get around 17 miles per US gallon in my 1933 pushing its little 189.8 cu.in. engine pretty hard with my 4.375:1 rear end in a car that makes yours look like an aerodynamic dream. Quote
greg g Posted June 13, 2011 Report Posted June 13, 2011 (edited) inside the carburetor is an enrichment valve that take over for producing sustained power after the accelerator pump has delivered its squirt. It depends on a vacuum sigal from the intake manifold up through the body of the carb to keep it closed against a spring. It works by pulling a tapered eedle out of a jet. As intake vacuum drops the spring pushed the needle out of the jet keeping the mixture enriched until manifold vacuum is restored by resuming cruising speed. If it does not recieve its vacuum signal or is stuck from dirt or old gas, it will supply gas all the time. This can negatively effect your mpg by 3 or more mpg. Have you examined your spark plugs to see if they are fuel fouled, or ashy? There should be a slot in the gasket that aligns with a small hole in the bottom of the carb base. They must communiicate in order for the vacuum to reach the plunger and hold it down against the spring. not doubting your math but how did you determine your mileage? One positive way, run it out of fuel, put in 10 gallons, record the odometer reading, drive it till it's empty, and see how many miles you have driven. Carry a full gas can if you test it this way.... Your timing setting can also effect your mileage. Is your choke opening completely, is your air cleaner flowing freely? Edited June 13, 2011 by greg g Quote
1940plymouth Posted June 13, 2011 Report Posted June 13, 2011 Paul. Welcome to the best flathead MOPAR forum there is. Sure would like to see some photos of your P-9, as I have a P-10 Greg and AndyDodge have covered the bases for you, hope you find the problem, Bob Quote
41/53dodges Posted June 13, 2011 Report Posted June 13, 2011 dont think anybody's said this yet, but check your fuel pump. ii used to run a stock one, but the diaphragm went bad and started pumping fuel into the crankcase, this happened to somebody on the truck side of the forum, and it ruined their engine. if the oil smells like gas, then dont question it, check it! Quote
Don St Peter Posted June 13, 2011 Report Posted June 13, 2011 I also have a P-9(original), with professionally overhauled carb and have been dealing with 9 to 10 MPG for over 2 years. All the things mentioned here I have checked as OK with no improvement in milage????? I burn regular gas with 10% eth. as I was told the flathead 6 could easily endure the higher temp. Should I be concerned and I do not think I could get non-eth. gas? Don Quote
greg g Posted June 13, 2011 Report Posted June 13, 2011 gas with alcohol in it looses BTU's and burns cooler than just gas. one other thing to check is any vacuum leaks between the garb and the engine, as runing lean will cause higher uder hood temps and decreased mpg. Quote
Plymouth 40 Posted June 19, 2011 Author Report Posted June 19, 2011 Thank you all for the reply's ... That dragging brake part that could's be a problem ....... I renewed al the wheelcilinders and brake lines and overhauled the main brakecilinder . The problem i noticed now is that sometimes the brakepedal gets as heard als a wooden stick so pressure is been build up and i can only relieve it when ik adjust the push rod of the brakecilinder. Than the problem is gone for a while buts its getting back sometimes whitin a day .So thats strange . i will try to disamble again the headcilinder but maybe i have to renew it. When i am honest its not so easy to adjust the brakeshoes of a plymouth . In the manual they use an sort of divice to adjust them . ofcourse there is no sudge tool available in Holland so we have to do it on our " feelings" Are there any other way''s to adjust them? regards paul, here some pictures of normandie Quote
TodFitch Posted June 19, 2011 Report Posted June 19, 2011 ...The problem i noticed now is that sometimes the brakepedal gets as heard als a wooden stick so pressure is been build up and i can only relieve it when ik adjust the push rod of the brakecilinder. ... Sounds like the rod from the brake pedal to the master cylinder is adjusted too long. If you look in the master cylinder you will see two holes. There is a very small one that the piston cup must retract back past or you will build up pressure and have the brakes lock. Quote
oldodge41 Posted June 19, 2011 Report Posted June 19, 2011 This brake adjustment procedure worked best for me on my '41 Dodge. It does sound like the rod that activates your master cylinder is adjusted too long though. There should be a little free play at the pedal before the piston in the master cylinder moves. That would explain your hard pedal and brake drag issue. http://www.ply33.com/Repair/brakes Quote
greg g Posted June 19, 2011 Report Posted June 19, 2011 also make sure that the pressure relief port in the bottom of the MC is open and free of debris. There are two holes in the bottom of the reservoir, one to feed the piston, and one to allow the fluid to return when the pedal is released. make sure both are visible through the fluid as see through the filler cap. Also allow some space in the reservoir, don't completely fill it. Today I made a 182 mile round trip to attend a car show. I used 9.8 us gallons of gas for just over 18.5 mpg, this on regular roads with speeds from 45 to 60 mph. I think I need to replace my points as they have about 10K miles on them. Is this the pic you wanted to post? Quote
Plymouth 40 Posted June 20, 2011 Author Report Posted June 20, 2011 Hi Greg yep that was the picture ?? how did you do that .. ?? I tried to make it visible but without any results.. Ill take out the masterbrakeclinder and check it again ! It must be something inside that cilinder that obstructs that hole regards Paul Quote
greg g Posted June 20, 2011 Report Posted June 20, 2011 when you post oictures use the go advanced button and the preview post feature, this will show you haow your post will look on teh forum. by right clickig on the red x in your post, I found thet the copied link was corupted by some exra letters. You had http://https//picasaweb.google.com/lh/photo/nMac5uZC8sm9DQ0XpFpOfJh3uVlCm2mlmbWF7NUkKK4?feat=directlink by deleting the "https//" then copying that into my browser it took me right to your picture so I reposted it with the correct address. If you use the Image tool in the toolbar of the dialog box it already contains the "http://" so when you copy and paste your photos, address do not copy that part or edit it out of the work box before you post it. You should't need to pull the MC. Remove the cap and shine a light down through the Brake fluid, you should be able to see both holes. The inlet is about the size of a #2 pencil lead, and the relieve port is about the size of common mechanics wire or a medium paper clip. If you have either piece of wire you should be able to clear the blockage without pulling the MC and then having to rebleed the brakes. Quote
Plymouth 40 Posted June 22, 2011 Author Report Posted June 22, 2011 Hello Greg, Thank you for your reply! Here finally a few pictures more of Normandie, Ohama beach monument St mere eglise Ohama beach at 21:30 PM Bayeux . Paul Quote
greg g Posted June 23, 2011 Report Posted June 23, 2011 Car looks great, looks like you got the process down pat. Thanks for the pics, Have you had any luck with your fuel usage situation? Quote
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.