Diesel injection pump pressure test ?

For a good test you need the injector out of the engine, this enables you to determine if the spray pattern is OK or if any dripping is occurring. This test is normally done with a hand operated pump.

Jack

That's for testing the injector, it sounds like he wants to test the pump itself.

I want to test the pump pressure itself ( at least get a good idea as to whether it is going bad ) not the injectors .

As far as I know the usual failure of an injector pump is a lack of uniform delivery due to wear of the rack and associated parts rather than low pressure. The injectors are usually the first parts to need replacement due to erosion of the needle and spray orfice. With good injectors in place and no other faults (properly operating valves, no intake leaks, passing a compression test, correct injector pump timing) a rough running diesel or one down on power or throwing black smoke needs an injector pump rebuild.

Having had three diesel engines, I would recommend taking it to a diesel shop (e.g., Seattle Injector, in Seattle) for testing. I really think that test you (or I) would do would be inconclusive or darnright wrong. Injection pumps don't often go bad. Air in the lines is bad.

Tom

If you have a way in, a guage that reads the pressures desired & the specs your already there. Most of the 7.3s I see have an extension of some sort on top of one of the injectors (usually right front) that screws onto the top of the injector, then the line screws onto that. If you had one of these (from a junkyard) you could tap threads into the side of it to accomodate your guage & it would be a bolt in/ removable situation so you wouldn't have to destroy anything in the fuel system to tap in.

Injector pumps are positive-displacement things, so you absolutely must have a way for the diesel to get out. If you stuck the gauge directly to the end of the line you'd break something. Probably the gauge, but no guarantees it won't ruin the pump. You cannot tee-in to the fuel line either. Besides the lines being too stiff for you to make room for the tee, the volume of that line is calibrated. Changing it will throw off the pressure your fuel pump develops when injecting, so your measurements will be meaningless. If the pump cannot develop enough pressure to run the injectors due to wear you'll have hell even starting the engine. But that shouldn't ever happen unless it's been fed bad fuel. Your pressure is controlled by the injector needle, not the pump--it just builds pressure until that needle gives. Before pulling the pump what you need to do is bench-test your injectors as another poster described. Or test them in the engine: If your problem is rough running from a single bad cylinder, then with the engine running, crack each fuel line loose (one at a time) and see if diesel fuel is spilling out to make sure that cylinder is getting fuel. Crack it at the injector end, so you don't wind up letting an air bubble into the fuel line. You may even let out an air bubble in there already. Also listen to the engine, if there is no change to the engine sound/RPM when you crack it, or you start with a loud hammering sound that goes away when you crack the line, you've isolated the bad cylinder. Swap that injector with any other injector in that engine and run the test again. If your problem moved when you moved the injector, the injector is bad--replace or rebuild it. If the problem stayed in that cylinder, then you either have a problem in the pump or you have a mechanical problem, like a valve setting. Do the usual mechanical checks on the engine. If the engine's good, it's the pump. Once you narrow it down, you can decide what to do. Checking the pump's performance any further requires some hideously expensive equipment and is done off the engine. If you find a problem with the pump you might as well pull it and take it to a pump shop for a rebuild.

The best way is to remove the pump and attach it to a test arrange to check for all of fuel delivery aspects.

Regards,

Ralf

Yep. Bench test, calibrate and time it. FWIW the injector crack-off pressure is probably many times 3000psi. and it is more likely that your injectors need service, although mechanically controlled pumps do have an awful lot that could go wrong, especially if it has automatic cold start, temperature and altitude compensation etc.

Huw