INJECTORS

[DianeD]

Still have low fuel pressure. Diesel engine will not run. Just put in new pressure relief valve and spring. How much pressure should you have at the injectors if the pumps are working right? Thanks!

 

[DianeD]

Sorry, forgot to mention this is about the injectors in a CAT 1953 D-4 Dozer.

 

[Anonymous-0]

A good operating fuel transfer pump should put out 15 psi fuel pressure. Did you check the condition of the seat for the pressure relief valve plunger?
The breaking pressure on injection nozzles is 800 psi max and questionable at 500 psi or under. Injection pumps and nozzles need special equipment for checking other than nozzle spray pattern which can be checked by hooking them up outside the pre-combustion chamber. Caution here as the pressures are high enough to penetrate skin.

 

[DianeD]

The seat for the pressure relief valve was good.The pressure barely comes up in the red. The only way he can get the pressure up is to use air compressor. We checked the injectors and all we got was drips.Don't know if it's the transfer pump or the injection pump or something else. How much does an injection pump cost? Thanks!

 

[Anonymous-0]

The injectors and injector pumps will not work unless you have assured adequate transfer pump pressure and delivery. You need to sort out why you are not getting adequate pressure. It's either worn out transfer pump or blockage. Did the top cover gaskets on the fuel tower get installed right? Any leakage from the tell tale drain line coming from the shaft seal area of the transfer pump? Has there been any indication of oil level rising in the main engine sump?

 

[DianeD]

He thinks the top cover gaskets on the fuel tower are installed right.Did not notice any leakage from the drain line and no oil rising in the main engine sump. Thanks!

 

[Anonymous-0]

Even more specific...
Did you use Cat gaskets for the filter deck and cover or were they home made? Did you use #2 permatex gasket sealer (sparingly) or that nasty silicone stuff. Being how all this occurred just after a filter change I would suspect blockage in the fuel delivery tube (which is kinda small) going past the gage tap and on to the injection pump manifold chamber (which is fairly large). I'd open the filter housing back up and check for port blockage at the gaskets and blow out the delivery passage with the gage connection removed. Also open at least one of the injection pump vents and blow air through the filter delivery tube and through the open vent to make sure everything is clear.

 

[DianeD]

They are the good CAT gaskets. He is getting good fuel to the injector pump,but when he tries starting the diesel engine he can take one of the injector lines off and put his finger over it and hold the pressure with his finger.This is using air to get the fuel pressure up.With no air it will only come up in the red. Thanks

 

[Anonymous-0]

First off.......don't be checking for pressure that way. When working the injector pump (one for each cylinder) is capable of blowing a hole through your finger.

Take the side cover off the injector pump housing and check to see that the rack is moving when you open throttle. This is not a direct linkage connection and depends on spring force to move it. Common to have them stick and in the closed position you get no fuel delivery to the injectors. Still requires decent transfer pump pressure and flow to charge the injector pumps.

 

[Anonymous-0]

If all was right, it would be working......if you are correct that leaves nothing left but a worn out transfer pump. You can either dismantle the pump and check for clearances as I already described or swap out for another pump and see what happens.