Injection pump seal leaks and cold starting gets worse

A long-running Spanish-language owners' forum thread devoted to this engine's injection pump describes it as a defect the engine simply has, with one experienced member writing that they all come to it sooner or later, and warning that a truck left with the worn seal will fail to start cold and will get worse each time. A buyer's guide for this generation names the same thing more briefly, listing injection pump seal leaks among the fuel-system items to expect and attributing them to ageing seals. The two agree on the shape of it: this is a wear item on a mechanically injected diesel, not a design catastrophe, and the seal itself is a cheap part. What makes it worth its own entry is the gap between that part and the bill. The forum thread's whole point is the gap between the two: the seal itself sits at the very bottom of the cost band, and the quote the poster was given for the same job sat at the top of it, because getting to the seal means the pump comes off and goes back on, and a distributor pump that goes back on wrong does not run. The fix path below carries the whole span as a band rather than a figure, which is the only honest way to state a price that depends on your market, your currency and your year — where you land inside it is decided by who does the work, not by the part. The cold-start-only pattern is what points here rather than at the glow plugs, which fail with the same complaint and are far easier to check first. Diesel around a hot engine is a fire risk: if you can see fuel dripping rather than a damp film, that is a different and more urgent problem and the truck stops until it is fixed.

Gen 2Gen 2.51993–1999Can strand youCommunity consensusSafety-critical

Drive gently — repair soonManeje con cuidado — repare pronto

Safety notice — Fuel system.

This affects a safety-critical system. Reference material only: for safety-critical work, consult a qualified mechanic.

Esto afecta un sistema crítico para la seguridad. Material de referencia únicamente: en trabajos críticos para la seguridad, consulte a un mecánico calificado.

Community consensus. This entry is not backed by factory documentation — treat its values and steps as a starting point, not as if they came from the factory manual.

Consenso de la comunidad. Esta entrada no se apoya en documentación de fábrica — tome los valores y los pasos como punto de partida, no como si vinieran del manual de fábrica.

Symptoms

It starts harder from cold every few weeks, on a curve that only goes one way
Starts on the button when warm and fights you every cold morning
A damp, dust-caked film of diesel around the pump and down the block below it
Long cranking before it catches, sometimes with a puff of white smoke
Rough, uneven running for the first minute and then normal

Likely causes

Worn shaft seal in the injection pump
Air drawn in through a fuel line, a filter seal or the filter housing
Worn glow plugs or a fault in the glow circuit
Worn injectors no longer sealing or spraying properly

Diagnostic steps

Degrease the pump and the block below it, run the engine, then look again the next day for a fresh film and follow it back to its highest pointPoints toWorn shaft seal in the injection pumpRules outWorn glow plugs or a fault in the glow circuit
Test each glow plug and the relay that feeds them before anything is taken off the pump, because they produce the same cold-start complaint for far less moneyPoints toWorn glow plugs or a fault in the glow circuitRules outWorn shaft seal in the injection pump
Watch the clear section of the fuel line, or fit a clear hose in the supply, and look for bubbles travelling towards the pump while it runsPoints toAir drawn in through a fuel line, a filter seal or the filter housingRules outWorn injectors no longer sealing or spraying properly
Have the injectors removed and tested on a bench for opening pressure and spray patternPoints toWorn injectors no longer sealing or spraying properlyRules outAir drawn in through a fuel line, a filter seal or the filter housing

Fix paths

Replace the pump shaft seal and its O-ring

$–$$$Difficulty 5/5

The parts are inexpensive; everything else about this job is not. The forum thread's own account has the pump coming off, the seal and its rubber ring changed, and the pump going back — and it ends by stressing that the fuel filter must be primed properly afterwards. A distributor injection pump is timed to the engine, and refitting it wrongly leaves you with a truck that will not run at all. If you cannot re-time a pump, this is work for a diesel specialist.

Find the air leak and prime the system properly

$Difficulty 2/5

Cheapest first: a hardened filter seal or a cracked supply hose lets the fuel drain back overnight and gives exactly the cold-start complaint the pump seal gives. Change the filter, renew its seals, prime it fully, and see whether the next cold morning is different.

Renew the glow plugs and repair the glow circuit

$–$$Difficulty 3/5

Do this before the pump comes off, not after. Plugs are replaced as a set, and the relay and its wiring are checked at the same time, because a good set of plugs with no current reaching them behaves exactly like a bad set.

Have the injectors tested and serviced

$$–$$$Difficulty 4/5

Worn injectors dribble instead of atomising, which shows up worst on a cold engine. Testing is a specialist's bench job and it is worth having all of them done together so the engine is even afterwards.