Previous information and explanation in my Trade Seminars on EFI fuel pump failure resulted in a number of members requesting further information on the subject to publish this information onto the INTERNET for members access.

The most likely cause of a fuel pump failure is:-
1. Blocked or dirty eveporative system ( Charcoal canister) | see why |
2. Blocked fuel filter,  | see why |
3. Water in the fuel. (causing resin and rust)  | see why | 
4. Solid particulate contaminant (in a word, dirt) or gum residues from oxidised fuel.| see picture |
5. Blocked pre filter sock or strainer,  | see why |
6. Bad earths, voltage drops from the pump relay, | see why |
7. Driving the vehicle too often on very low fuel quantity, | see why |
8. Old age, the pump is on the end of the 100 000 km performance expectancy | see why | 

Ask yourself the question:

" What caused the last pump to fail?"
If it failed due to dirt, rust, scale, oxidised fuel or other contamination, just replacing the pump won't cure the problem.

This is a tank ventilation and filtration unit in a closed loop from the fuel tank towards the vacuum source of the engine. Due to the anti-pollution legislation, all cars must now be fitted with a single or dual stage charcoal canister. HC, or fuel fumes must not enter the atmosphere. Instead they will be sucked off into the engine's intake manifold via a purge valve on the charcoal canister.
| see picture |

If the fuel tank slowly becomes empty, the vacuum from the fuel tank sucks air back into the fuel tank via the purge valve from the engine manifold or the vent, to replace the empty space of the fuel which has been used up. The purge valve is a pressure or vacuum equaliser, operated by a diaphragm and seals. The charcoal in the canister is used as a filtering compound for liquids like petrol, vapour and fresh air. ( which my contain road dust!)

Petrol may enter from time to time when the fuel tank is over filled and the vehicle is left in the sun on a hot day. Fuel will expand and follow the breather line into the charcoal canister. On rainy days the overall humidity is about 98% which passes via the filtration of the charcoal canister back to the fuel tank. The continuous moisture and heavy road dust filtration over the years makes this unit internally look like an engine with a severe head gasket leak, with grey to black slime inside the tappet cover. This brings the charcoal canister out of service for tank ventilation.

Expanded fuel which is mixing with this dirt each time the fuel tank is over filled, is then drawn by negative pressure back into the fuel tank. This extremely discolours the fuel on the first return flow and the fuel pump pull’s all that abrasive dirt trough the pump rotor and stores that dirt into the fuel filter.

Excessive vacuum build up inside the fuel tank will restrict the fuel flow and pressure. By removing the fuel cap, a big air suction or air pressure from or into the tank is the result of a blocked tank ventilation which may also be caused by a kinked vent line to the charcoal canister. Checking the charcoal canister operation is quite simple with the INTER-JECT LB-291/F or 2F.

Connect the servicing instrument in series into the fuel supply line. Close the diversion valve and start the vehicle. Using a 20 litre container, connect a diversion hose to the valve outlet and insert the hose into the 20 litre container. Open the diversion valve to a point of 40 l/h on the flow meter indicator. See if the flow changes to 35 or a lower indication before the 20 litre container becomes full.

Remove the tank ventilation hose from the charcoal canister and at the same time see the flow increase on the flow meter which returns to 40 l/h. The service instrument is telling you;
CHANGE THE CHARCOAL CANISTER as it is blocked.

2. Blocked or restricted Fuel filter:

From the charcoal canister, the dirt is now entering via the fuel pump into the fuel filter.
Fuel injected cars always have a circulating fuel system. That is, the fuel goes in a circle, up to the injectors and back to the tank to cool the fuel pump, fuel rail and the extremely delicate injector wiring from overheating all the time the engine is running. This prevents also vapour lock. EXCEPT of course when a hot engine is left standing. In this event the problem soon rectifies itself as cold fuel cycles through the system as soon as the key is turned.

The VL Commodore has an additional device called a FUEL PRESSURE REGULATOR CONTROL SOLENOID VALVE or FPRCSV located at the back of the head. When the engine temperature is over 95 degrees C the solenoid opens for four minutes when the engine is started. This allows atmospheric pressure to go to the fuel pressure regulator. The resulting increase in fuel pressure clears any air locks.

CASE HISTORY:
A smouldering carpet was caused by an apparent short in the wire to the fuel pump. The slow blow fuse was replaced with a regular fuse but this blew after the pump was turned on. There was no alternative but to check the fuel pressure and flow from the fuel pump with the LB-291/2F.
It revealed very low fuel flow. The fuel filter has been blocked causing very high pressure between fuel filter and pump and overloaded the pump causing the fuse to blow and wiring to overheat. The pump ran for some time out of alignment and lost its performance. A note to the customer of this occurrence is highly advisable, as this pump is now in a free spin after a new filter change and may fail.

In-tank pumps only: Nissan and some Toyota's using pump voltage changes timed to de-load the pump flow after 20 seconds if at idle. Soon the TPS is moved off idle, the pump spins faster providing the flow back to normal. There is no fuel pressure change at all, (only flow) as the regulator controls the pressure to operating pressure even if the flow is only 5 litres an hour or less.

Overheating of the pump cause to snap the plastic coupling between the Rollercell and the pump motor. The overall dangerous point of a blocked fuel filter is, that the plastic pump end cup housing the motor brushes and the material used in the Rollercell end cap has a melting point of
230ø to 260ø C. | see Picture of rollercell and pump rotor |

LPG/ dual fuel systems:

All aftermarket dual fuel systems do not have a switch to stop power going to the petrol pump when running on LPG. The reason for this is to prevent the INJECTORS from overheating, melting plastic bushes internal seals, coil laminations etc. destroying the Injectors. | see picture |

Make sure that the pump is always running, cooling the rail and injectors to transfer heat off from the Cylinder Head via the recirculating fuel !!!

Allowing a pump to run with little or no fuel will cause the pump to overheat, leading to build-up and formation of gum within the pump housing and higher than normal amperage draw, resulting in a meltdown of the brush housing.   | see picture |

INTERJECT is recommending that any dual fuel system operate on a minimum of 1/4 tank of fuel threaded with 250 ml INTER-JECTRON and be started on petrol at least once a week to minimise Injector-pintle and pintle cup to a partial/ or full carbon closure.

To unblock an injector from a gas converted engine:- Soak the Injector for a minimum of 3 hours in the INTER-JECT Cleaner. The Injector will flow again.

Electrical checks:

Many pumps that have suffered a partial seizure or pressure overload by a blocked fuel filter will draw more amps and will continually blow fuses. | see why | Therefore, it is common practice to replace the fuse with a larger fuse in the pump circuit to force the pump into operation. This can cause excessive current draw and higher than normal temperatures within the pump, melting the brush cover assembly and damaging the vehicle wiring and something no one discovered yet, is the fuel pump relay contact points burning causing a voltage drop to the pump.

If the pump fuse is other than original specification, replace it.

Installation:

As repairers, we need to be satisfied that the fuel tank, rubber fuel lines, filter, fuel rail and regulators, do not contain foreign matter that could contaminate the system. When assembling the new fuel pump in the hanger assembly (in-tank pumps) ensure that the pre-filter/ strainer is correctly positioned and seated all the way home.
Remember: Keep your work benches clean when assembling fuel pump components!
" The new pump does not get a second chance."

Check the following areas if engine is not starting:

• Power at the fuel pump fuse/relay (note: do not replace the fuse with a higher amperage fuse as this will induce further problems);
• a good earth from the fuel pump to chassis;
• petrol in the tank - is the swell pot pushed up, tank damaged, bend upwards near the swell pot, gauge working condition?;
• is the rest of the fuel system in good working condition? What about the Charcoal canister??;
• is there sufficient flow and pressure to run the engine ?;
• and last of all, can you hear the pump working when you turn the ignition on as the system is pressurised? With the exception of some vehicles with mechanical air flow meters containing fuel pump activation points. ( Toyota Camry ect.)