Problem starting mc8 w/ 8v71

[SeanM]

Hello forum. I'm a newbe, so please bare with me. Don't know much about this stuff. I just purchased a 76 mc8. Not able to get it started. traced the fuel from tank to filter, then to pump, replaced pump. I'm getting fuel. Also PO installed a Holley fuel pump in it as well. not sure why maybe to help priming    motor cranks from rear with panel.but that's it. able to get it running with starter fluid. Just won't stay running. Really not sure what to do. Need to get it operational to get it 30 miles where it will sit while worked on.  Any help would be greatly appreciated.

[lostagain]

Likely just  needs priming. Run the electric pump until you hear a change in tone, indicating that it is pushing fuel against full lines. Keep it running while you crank. You can turn it off after it runs.

JC

[Bill Gerrie]

Watch for fuel to return to the fuel tank. It is visible while looking in the fuel fill opening. You should see a stream of fuel flow back to the tank when the system is full.

[robertglines1]

front Ign switch needs to be on also.  Where injector pump shut off is there is a air operated cyl. Make sure it is not extended. Two Phillips screw hold it in place. If one were removed it could be turned sideways and let injector pump provide fuel to engine. (not able to recommend) also make sure shut  off air flapper on blower is not tripped and needs to be reset(a manual reset) there is a switch in front that sometimes get flipped by accident---this requires manual reset on side of blower..Let us know where you are and maybe someone can swing by and help. Look up Detroit diesel emergency shutdown.

[SeanM]

The bus is in Tampa, Florida. I have 3 weeks luckily to get it moved. Hopefully I get it up and going by then. 

Lostagain: I have tried starting it with the electric pump on and off. have let it run (pump) for quite awhile before trying to start the motor an still a no go.

Bill: didn't think to look at the fuel return line to see if there is flow going back into the tank. Will be trying that tomorrow. Also read in a Manuel that there is a valve under the head cover that needs to be loosened to bleed the system. this true? if so what valve is it referring to?

Robert: yes the ignition switch is on in up front. makes a chime when on. You said injector pump shut off where is that and what does it look like  are you referring to the cylinder on the governor? I have seen the tab on side of air inlet to mover flap open or closed. however don't see anything to reset on it.

thanks for everyones quick response. hope to get this going sooner than later. as I'm sure there are other system I don't know about yet I should check before even driving it once motor works.

the first pic is what I see as far a tab for the  air intake flap. but no way to reset anything? the second photo is of the tab as well as the cylinder I think you are referring to (probably wrong though)

[SeanM]

Also don't have the air intake can. Anyone know where I can get one or something close that will work? Tried Luke at us coach waiting for call back. Is there another option out there?

[Bill Gerrie]

The yellow circle in the second picture is the emergency shut off flapper and the other is the shut down solenoid that cuts off fuel to stop engine. It looks like it is retracted but if no air in system it will be retracted. The emergency shut down flapper will sometimes seize so look in the air horn to make sure it is open to the blower. Luke is probably your best bet for the air cleaner. You will need a large rubber boot to join to the air intake from the air cleaner.

[robertglines1]

looking in engine rear door look left below Radiator /above frame level. Is there about  a 2 1/2 ft tall can shaped thing prob 18 inch diameter= air cleaner. If not there I would look for a eco filter with correct ID to attach to air horn I'm sure 1000cfm would be sufficient..   The emergency air damper is manual reset by basically twisting until it clicks back in place. From looks the shutdown cylinder is new/maybe trying to solve problem you have now. 8-71 has a restrictor in return line that must be there. (if not all your fuel will just return to tank) instead of pressuring the injectors to spray. Also in your picture is a fuel switch that is controlled by oil pressure etc.  For  test  purpose take wire off it.  Do you have a  mechanical oil pressure gauge mounted about where the Holley pump? 

[robertglines1]

some one with good eyes is that fuel pump (elect) plumed into return line?

[freds]

Had a recent problem with a mechanical lift pump loss of prime issue with my diesel generator; in that the problem was a loose valve inside of the pump.

You should not have to add an electric pump to assist with keeping prime (unless you run the tank or filters dry), though you could use it to pump in to a container to make sure that fuel delivery is working and not sucking any air into the line in the process.

Do this by submerging the output end in a bucket and pumping a full gallon, also should not take too long to pump that amount of fuel.

[Scott & Heather]

That's definitely your shut off. Make absolutely sure that little air piston stays retracted when you are trying to start the coach.

Also, that lever it pushes on sometimes gets stiff so manually make sure it's pushed as close to the retracted air piston as possible.


As someone mentioned, if you can't find the air cleaner can, then measure the diameter of the air intake horn I see in the photo and purchase rubber unions and maybe even some intake piping and extend it out far enough into the engine bay to clamp on an ecolite air filter. I use one on my 8v92 and it works perfectly. They are disposable filters built inside their own can.

Here's a source for the pipe and rubber. You're probably looking at 5" diameter stuff but measure yours to be sure:

https://www.truckpipesusa.com/categories/air-intake-exhaust.html

Here's a source for the air filters I use and you could use this exact model on yours if you wanted to:

Luber-finer LAF7455 Heavy Duty Air Filter https://www.amazon.com/dp/B0049LS4CC/ref=cm_sw_r_sms_c_api_i_qQEMDbC2QZ2DA

[SeanM]

I have let the elec pump run for some time now. I don't appear to be getting a return to tank. I will probably get one of the eco filters. mine doesn't have the large can assembly. It's all missing. the shut off seems to be as close as it will turn to the piston. can't get the piston to move in any.

[SeanM]

looking in engine rear door look left below Radiator /above frame level. Is there about  a 2 1/2 ft tall can shaped thing prob 18 inch diameter= air cleaner. If not there I would look for a eco filter with correct ID to attach to air horn I'm sure 1000cfm would be sufficient..   The emergency air damper is manual reset by basically twisting until it clicks back in place. From looks the shutdown cylinder is new/maybe trying to solve problem you have now. 8-71 has a restrictor in return line that must be there. (if not all your fuel will just return to tank) instead of pressuring the injectors to spray. Also in your picture is a fuel switch that is controlled by oil pressure etc.  For  test  purpose take wire off it.  Do you have a  mechanical oil pressure gauge mounted about where the Holley pump?

is this the switch you are referring to for test purposes? I don't appear to have a mechanical oil pressure gauge mounted by Holley pump.

[SeanM]

better look at the bypass to the elec pump. the two yellow ring lines are what feed the pump.

[edvanland]

did you put new fuel filters on?