P38 diesel fuelling issue?

[cpa]

Cold starting problem. Having problem starting - eventually starts after cycling the glow plugs on three times then catches but then revs hunt up and down finally rests at normal. Lots of smoke out the back. Replaced battery, glow plugs, alternator, engine temp sensor and timer relay. No air in fuel feed pipe. Problem when engine hot or cold. Have a hot fix box fitted which is operating properly. Any ideas what next to look at?

 

[wammers]

Cold starting problem. Having problem starting - eventually starts after cycling the glow plugs on three times then catches but then revs hunt up and down finally rests at normal. Lots of smoke out the back. Replaced battery, glow plugs, alternator, engine temp sensor and timer relay. No air in fuel feed pipe. Problem when engine hot or cold. Have a hot fix box fitted which is operating properly. Any ideas what next to look at?

Check static timing. There are plugs not working. How long is the glow lamp lit on a cold morning?
Which temp sender?

 

[cpa]

Check static timing. There are plugs not working. How long is the glow lamp lit on a cold morning?
Which temp sender?

 

[cpa]

Replaced the green temp sender - the one with two wires going into it. Timer relay coming on for 5 seconds on a cold morning. New relay made no difference to timer duration. Wondered if hot start box causing over fuelling ?

 

[Mark Piercy]

have a look at your fuel pump on the engine with a torch. I have leaking seals on mine that sometimes gives a stutter on start up. Wammers, what is this hot box we speak of?

 

[wammers]

Replaced the green temp sender - the one with two wires going into it. Timer relay coming on for 5 seconds on a cold morning. New relay made no difference to timer duration. Wondered if hot start box causing over fuelling ?

Should be on for more than 5 seconds on a cold morning very cold should be 8 or 9 minimum. Disconnect the hot start and see what you get. Timing is controlled by ECU subject to readings from ECU temp sensor. (The green one) Glow relay is just that a relay, switched on or off by ECU. If you have a stuttering start and smoke that would tell me some of the glows are not working.

 

[wammers]

have a look at your fuel pump on the engine with a torch. I have leaking seals on mine that sometimes gives a stutter on start up. Wammers, what is this hot box we speak of?

Hot fix is a box fitted to trick ECU into thinking engine is cold, so putting on glows and giving cold start fuel settings when engine is hot. Usually but not always means static timing is retarded so hot starts suffer.

 

[Grrrrrr]

Probably worth checking what your in-tank lift-pump is doing. There's a test in the how do. Diagnostics would help.

 

[wammers]

Probably worth checking what your in-tank lift-pump is doing. There's a test in the how do. Diagnostics would help.

The smoke is unburned excess fuel being ejected from the exhaust because the glows are not working and the fuel is not being burned on certain cylinders. Giving lumpy running until they chime in.

 

[cpa]

I did wonder about the hot start fix - I'll disconnect it and see what happens. All the glow plugs are new and good quality. Tested the old ones when out of engine and they all worked a treat - so that was a waste of £50! The voltage at the plugs is around 10v so maybe that's it? No idea where the earthing straps are tho.

 

[Wazzajnr]

I did wonder about the hot start fix - I'll disconnect it and see what happens. All the glow plugs are new and good quality. Tested the old ones when out of engine and they all worked a treat - so that was a waste of £50! The voltage at the plugs is around 10v so maybe that's it? No idea where the earthing straps are tho.

10 volts would suggest to me that they're not getting enough volts so probably not getting hot enough.
There should be close on Vbatt across them when they're on. (will be slightly less due voltage drop but not by over 2 volts

 

[Mark Piercy]

Hot fix is a box fitted to trick ECU into thinking engine is cold, so putting on glows and giving cold start fuel settings when engine is hot. Usually but not always means static timing is retarded so hot starts suffer.

i dont have one of those! No issues with starting either.

 

[Grrrrrr]

i dont have one of those! No issues with starting either.

They changed the later models. IIRC correctly later models keep the in-tank pump running. Also, the map where it thinks the engine is running has lower rpm so when starter or battery starts to get tired it doesn't cut the fuel. Lots of tweaks that supposedly fix it. Issue common to the early M51 and discussed all over.

 

[Mark Piercy]

you know, thats puzzled me ever since i owned my omega diesel (bm engine 1999) that never had one either and after seeing the subject posted on their forums, I now have the answer! Your Grrrrrreat! Thanks

 

[wammers]

They changed the later models. IIRC correctly later models keep the in-tank pump running. Also, the map where it thinks the engine is running has lower rpm so when starter or battery starts to get tired it doesn't cut the fuel. Lots of tweaks that supposedly fix it. Issue common to the early M51 and discussed all over.

Lift pump runs when cranking on models after 1999, on models before that it only runs with glows or when engine is running.

 

[cpa]

So this morning took off the hot start fix kit. Freezing cold and the glow plug light only came on for 4 seconds. Spluttered into life after turning on ignition a couple of times. Started on the button after that. For some reason the BECM must be telling it to switch off plugs prematurely. Have already replaced temp sender with new one. So I doubt it is that. I guess the BECM needs to be interrogated to find out why such a short pre-heat?

 

[wammers]

So this morning took off the hot start fix kit. Freezing cold and the glow plug light only came on for 4 seconds. Spluttered into life after turning on ignition a couple of times. Started on the button after that. For some reason the BECM must be telling it to switch off plugs prematurely. Have already replaced temp sender with new one. So I doubt it is that. I guess the BECM needs to be interrogated to find out why such a short pre-heat?

Plugs are lit for varying lengths of time subject to engine ECU engine temp sender readings. The colder the read temp the longer they stay on. On a day like today mine will be on for 8 or 9 seconds. You need to get a Nanocom on it. If the engine ECU temp sensor fails a preset of 50 degrees is used, sounds like you may have fitted a duffer. ECU temp sensor is the green one between cylinders 3 and 4. On a pre 1999 car there are two sensors brown single wire, no aircon or blue blue two wire with aircon, behind injection pump. Green ECU temp sensor between cylinders 3 and 4. And on cars 1999 and up a black overheat sensor between cylinders 5 and 6.

 

[dubbleRR]

I would be looking at leek off pipes on injectors ....

 

[Mark Piercy]

hey wammers, I dont have the black sensor just a blanking plug?? Late 1999 model with aircon..I have the other two.

 

[wammers]

hey wammers, I dont have the black sensor just a blanking plug?? Late 1999 model with aircon..I have the other two.

If your car is MY 1999 it should have a black sensor around cylinder 5 and 6. This brings the aircon fans on to aid cooling in the case of an overheat. Has it had an earlier head fitted and the sensor has been left off. You should have a plug on the loom in that area. Check with Nanocom for the manufacture date. It should be listed with Vin number Etc. Can't find it on 1999 Rave but part number is STC2254 if you want to check application. Sure it came in in 1999 but maybe 2000. You have me thinking now.