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I have a self-built motorhome, Renault Master, 2003, with about 100k and a G9U engine, which does not start when I park it in the sun in the hot weather.

Part of this is due to the immobiliser ring becoming weaker (must be some soldering expanding) but I know when this is the issue because the immobiliser light will flash instead of being just on... When this happens, I don't even try to start it, I just turn ignition off and on again until the light goes back solid. I had this issue for about 4 years and I have found others with similar issues on this forum...

Recently however, I have found that the van does not start from cold in hot weather regardless of the immobiliser. When this happens, I can only start it by using a bit of easy start sprayed into the air filter.

Whether I start it normally or using easy start, when it first ignite there is a noise coming from the bottom of the engine, where the alternator and high pressure fuel pump is located - a belt noise, which eventually goes after a few minutes. I guess the belt is slipping somewhat and initially I was wondering whether this was the issue...

Anyhow, I took the van to our trusted mechanic and he found a leaky seal which he fixed for me but did not improve the situation and then a few weeks later he found that 3 out of 4 injectors failed the return flow test ie. they return too much fuel. We have had a lot of issues with injectors and leaky seals over the years and we even changed one about 6 month ago because it failed the same return flow test (so I deduce that these 3 failing now, were ok just 2000 miles ago), so it was not a complete surprise. On the other hand, the van, once it is running, it goes on full power, it never misses a beat and does not burn more fuel than usual...

Changing another 3 injectors is expensive and I am wondering whether it is worth doing... Apart from when the weather is hot, the van works. If I don't do them, will it get worse? Will it ruin other parts? We have spent a lot of money on injector, seals, re-threading and glow plug issues over the past few years... If this was the last bill that sorts the issue for good then I would bite the bullet, but I am worried it is not.

Mechanic mentioned that maybe he could take the injectors out and send them to be fixed. Is this as good as replacing them with new ones?

My other main concern is that other parts on the fuel line are on the blink (fuel pumps, etc.)... Mechanic seems sure that this is purely an injector issue and I trust him, however I still wonder, as before I took the van to him, I was inclined to think it would be one of the fuel pump causing the issue. Any thoughts?

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    Fuel injectors are a wear item but should not fail regularly. I could be wise to check the fuel system for contamination. Check if the fuel filter is in good shape and double check if there is no water that somehow got into your fuel tank. – MadMarky Aug 22 '18 at 11:43

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