Running Rich - Fuel Pressure Tests & Results

Further testing to investigate the rich running and high CO emissions I preformed a Fuel Pressure Test.

Set up - 8mm Female attached on fuel filter, Isolation Tap, T-Piece, Pressure gauge, Male 8mm to fuel rails.

Test 1- Static Pressure Test - Ignition on primed pressure pump runs for 2 seconds.

Pressure reads 2.5 Bar. Tap closed (isolating injectors & FPR) - 10 Minutes drops to 2.3 Bar. FPR Vacuum open (No idle under load conditions)

This confirms pump pressurises and holds without Vacuum applied (Low Vacuum, High load)

Test 2 - Fuel Pressure Regulator Test - Ignition on primed Pressure - Vacuum Applied on FPR

Pressure starts at 2.5 Bar. Tap Closed. Vacuum 24" Hg applied. Pressure Drops to 1.6 Bar and remains there.

This confirms that FPR regulator lowers pressure at Idle (High Vacuum, Low Load)

Test 3 - Fuel Pressure Regulator Test Repeat - Vacuum Applied then Ignition on primed Pressure -

Vacuum 24" Hg applied. Pressure starts at 1.6 Bar. Tap Closed.  Pressure Drops to 1.6 Bar BUT then decreases rapidly down to 0 Bar in <1 min.

This IS AN ISSUE as FPR should just lower the pressure. It seems that this test removes all pressure very quickly!

So I removed vacuum and repeated Static Pressure Test 1 and AGAIN it fell rapidly down to 0 Bar. Repeated again many time and all tests failed and static pressure was not held.

Conclusions:

So there seems to be some leak (Internal as no visual leaks found) not in the fuel pump circuit as tap was closed.

Did not have any more time to investigate but thoughts are:

1. Injector Leak - Through leak of stuck injectors - This would cause pressure to drop but not expected to be so rapid unless stuck open. This could cause excess fuel leaking causing rich mixture.

2. Fuel Pressure Regulator (FPR) - Stuck FPR spring or diaphragm - This would cause fuel to be returned. Thought if it was all being returned this would have caused a leaner mixture as less fuel pressure. Unless it sticks open and closed so increasing pressure causing rich.

Anyway I think I have found some issue.

I have ordered a FPR and also a set of 4 injectors (Not cheap! but at least I have them as spares as parts are getting scarce).

Further tests:

1. Repeat Pressure tests - Static and dynamic with engine running.
2. Dead End Pump Tests - Test pump pressure by dead end tests (turn tap & gauge round)
3. Repeat Tests above to recreate issue.
4. Isolate FPR - Clamp pipes or dead end FPR to see if pressure still decays.

I will most likely change FPR before injectors (much more work) and see if mixture returns to normal.

UPDATE:

No chance of getting injectors! Only available in South America market.

Ordered and fitted FPR - When removing FPR fuel leaked back from tank via return line which was odd.

Fitted new FPR and no difference to rich running indicated by Lambda.

Have not had time / cannot be bothered to rerun fuel pressure tests as I expect no change in rich running unless I can change injectors. 

Moved on to exhaust investigation....... See next post