Fuel Pump

[jream122]

I have 1989 2.0L (G63B), recently replaced mechanical fuel pump which is supposedly rated at 3.0 psi. I will say the old pump was suffering, and with the new one I seem to have more power, but fuel consumption has gone up more than expected. Fuel economy is important to me, and wanted to know if switching to an electric pump like the Carbole 42S would provide any real benefit for me.

[xboxrox]

Hello jream122

Cleaning the entire fuel system might be required ??

I'm 90% sure someone put contaminents in my fuel tank; my truck ran fine with rebuilt Mikuni replaced fuel pump & both inline and in tank fuel filters were replaced. Each step made my truck run better but then a nagging miss and eventually back fires running rough and now unsafe to drive on public streets.

I am in the process of rebuilding another Mikuni carburetor bought new oem made in japan fuel pump and plan to remove & clean the fuel tank then flush out the fuel lines with alcohol and replace new fuel filters again.

Meanwhile last month I installed a locking gas cap 3 blade type which allows the fuel door to close After the fuel system work I plan to install a 2nd lock on the fuel filler door PLUS a decent alarm system.

There is a small filter in the carburetor seat part of the needle seat assembly Mike's Carburetors has this filter & Amayama has the in tank filter & napa oreillys have the inline filter.

I try to keep my truck original but after this if I need more carburetor work I might go the Weber route and not worry if vacuum & electrical switches 'n selonoids 'n ECM work properly or not.

My Mikuni carb LESSONS LEARNED:
Check the float for leaks
Check solenoids for missing spring
Install new carb fuel inlet filter attached under & onto the seat of needle/seat assy
Clean but do not apply any sealer or grease to main wire harness to carb connector (any elec conn)

WHEW hope this info helps & Welcome to MR50 (TRUCK PHOTOS HELP)
George

[SubGothius]

Meanwhile last month I installed a locking gas cap 3 blade type which allows the fuel door to close After the fuel system work I plan to install a 2nd lock on the fuel filler door PLUS a decent alarm system.

Have you tried driving it with that gas cap off or left loose? I wonder if the cap needs to have a valve inside it to admit air intake as fuel is either depleted or contracts in cold temps, so if your locking cap is missing that breather valve feature, your tank could be developing a vacuum impairing fuel supply to the carb.

[xboxrox]

Have you tried driving it with that gas cap off or left loose? I wonder if the cap needs to have a valve inside it to admit air intake as fuel is either depleted or contracts in cold temps, so if your locking cap is missing that breather valve feature, your tank could be developing a vacuum impairing fuel supply to the carb.

1) The locking gas cap tested good (allows air in but not out) I lathered the cap's gasket & filler neck threads with NAPA brake silicone compound working good
2) I do not think anyone tampered with my truck I think I bought BAD GAS twice
3) I recently deleted the OEM fuel filter position & relocated a new filter in the eng bay
4) There were no bubbles in the fuel filter while it was in the original location
5) I discovered bubbles in the filter after it was moved to the engine compartment
6) Whats happening is the fuel is vaporizing into near vapor lock (an AHA moment)
7) I have a source for buying clean non ethanol gas soon will begin using it
8) I might relocate a smaller fuel filter between fuel pump & carb
9) I must rebuild the evap canister with new activated carbon
10) Might install a small fuel cooler near the fuel tank
11) The fix is to fight the vapor lock condition

[camoit]

Xboxrox

Sounds more like a bad jet valve.
A good place to buy good fuel is the local air port. 150 low led. It also has heat to make it burn hotter. Of course the led can screw things up if it has smog.
As for the original poster. A weber will always suck more gas.

[jream122]

This is great information. Thank you both so much. I foolishly neglected to mention that I have a Weber 32/36 DFEV Carb installed.

Funny that you mention the vacuum issue in the tank. I had been having problems with it until I swapped the mech pump out. Seemed like 1.5 to 2 hours of highway/highway speed driving followed by reduced throttle input (typically on the exit ramp) would be enough to overwhelm the pump and stall the engine out until I relieved the pressure in the tank. Tried changing the cap to no avail decided it may have been a issue induced by failing mech pump. Changing the pump seems to have fixed it but I am still building vacuum in the tank, so I am thinking filter or line is gummed up somewhere.

I believe it still has the original metal tank on it, was thinking of dropping that and having a look for contaminants. Fuel filter entering the carb looks clean, but figure it may be difficult to see rust. Is this the inline filter you are referring to or is there another? A quick look under the car in comparison to the service manual I purchased lead me to believe that some work had been done, filter removals and such. If I have the time in the coming weeks I think I will get it up on jacks and take a hard look what the issue is. Any additional tips/tricks would be appreciated!

[xboxrox]

SubGothius ~ the truck has not been driven since installing the (used locking cap from a neighbor friend) the truck ran good with the cap I swapped to neighbor & never has there been any air noises when opening that cap...

jream122 ~ yes there is another fuel filter hiding inside the fuel tank; remove the tank drain plug and the filter is right there on the drain plug... Go to my photo albums to see photos of the crud drained from the tank & installation of a new filter... Photos show the OEM part # that I bought from Amayama...

I think it's safe to say someone put contaminent (sp?) maybe sugar in the tank... No matter now it's just a huge & pricey fix & lottsa wrenching & the love of carburetor rebuilding... Katching $$

Sugar or other contaminents will eventually cause the gas gauge to indicate strange readings which began for about one week before we parked the truck as unfit to safely drive... The gauge only indicated about 5/8 tank when we filled up which normally makes the fuel gauge needle go all the way to the full line... Something is surely wrong; for a good while we had this truck running swell and getting 21 or 22 mpg... When last checked the mpg was down to 17 to 18 which is another indication of a contaminated fuel or entire fuel system...

[xboxrox]

Fuel system cleaning progress today: https://www.carparts.com/blog/have-s...es-what-to-do/

Confectioners sugar (powdered sugar) is worse than table sugar because it will pass through fuel filters..! (See link) Spent another $120.00 on gaskets Nuetral PH cleaner spray wand tool in line fuel filter...
Digging out supplies tools parts to put inside the truck prior to towing tomorrow...

Edit: I just realized the DORMAN 15gal fuel tank should fit & might only need extending my 18gal fill tube by an inch or two (will know after inspecting and measuring everything)... Would need to cut & insert a fuel resistant nipple into the cut fill hose ends then hose clamp the ends... Hope my tank can be cleaned & is not too rusty to reuse...

[xboxrox]

1) Camoit could be the Mikuni carb acting up but I think not (?)
2) Today the truck ran pretty much just fine a little struggle sometimes accelerating in 2nd or 3rd at low rpm or slow speed
3) No SMOG here in Hawaii & the trusted source of non-ethanol (E0) gasoline is the Kaneohe MCBH marina gas pump (fat nozzle means I must use 5gal can)
4) I've read the EVAP Canister can cause my issues Amayama checking if two they have might fit OR I will rebuild mine with fresh activated carbon
5) I cleaned & tested the vent/purge valve near the gas tank and blowing air thru it has made the truck run better (I need to adjust it 7° tilt towards the tank)
6) It makes sense to inspect clean test the entire evap sytem since it's operation can fight the fuel vapors forming in the fuel supply line to the fuel pump
7) Am running 89 octane ethanol (E10) purchased at the Kaneohe MCBH gas station ~ so far no bad gas from the base gas station
8) The ambient usual temperatures here in Hawaii contribute to high under hood temps & ethanol gas to vaporize ~ bubbles form even when starting cold eng
9) The MCBH Five O Motors (DIY auto repair shop) has a smoke tester machine which I will eventually use on the intake & evap systems
10) OK Elon these are ten things I've done today ~ hope I'm not gonna be fired LOL

Thanks for your time & support Marty

[camoit]

Jet valves cause backfire and loss of power. If you stick a vacuum gauge on it you will know instantly.

[xboxrox]

Jet valves cause backfire and loss of power. If you stick a vacuum gauge on it you will know instantly.

I believe it..!

We replaced the head w/o jet valves nearing two years ago now & three months ago a new OTC vacuum gauge held a rock steady 28 or 29 inches of vacuum...

NEXT WORK ON TRUCK WILL BE:
1) Replace mechanical fuel pump with oem made in Japan pump
2) Remove clean inspect test the. EVAP check vavle back near the fuel tank
3) Begin using clean fresh non ethanol gasoline 5 gallons (only) at each fill