Wont start after engine replacement

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weejangus
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Joined: Fri Apr 05, 2019 6:47 pm
Location: Scotland

Wont start after engine replacement

Post by weejangus »

Hi All,

As the title suggests, I've recently had the engine in my 1987 635csi replaced (old engine died last year!).

The garage have only been working on the car when they had some down time so I've been waiting nearly a full year to get to this stage.

The engine is in, wiring all connected up, and the car turn over - sounding very healthy but just wont start.

I remember from last year that I always used to hear the fuel pump priming when I put the key in Position 2. I can't hear this happening anymore so I suspected that was the issue. Tried jumping the relays but still nothing from the pump.

The garage have said that the problem is the Cold Start Valve. I've ordered a new one along with some fuel line at a cost of £170 - might as well replace the small section of fuel line while we're "in the area" - but would a bad Cold Start Valve prevent the car from starting at all?

Would that also give me the "fuel pump not priming" issue or should the fuel pump not be priming in position 2 anyway?

Wondering if it's a simple wiring issue when connecting everything back up. Is there anything obvious that we've maybe missed?

I would rather not continue throwing expensive parts at the car when we're not actually sure what the problem is.

Any help would, as always, be much appreciated.

Thanks,

Jay
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635sharknose
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Re: Wont start after engine replacement

Post by 635sharknose »

Did you check this topic on how you can check the cold start valve?
viewtopic.php?t=19899

Have you replaced the engine by a simular type of engine? Of the same year?
Did they make modifications to make it fit or was it plug and play?
Paul
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1987 635CSi Bronzitbeige
weejangus
Posts: 19
Joined: Fri Apr 05, 2019 6:47 pm
Location: Scotland

Re: Wont start after engine replacement

Post by weejangus »

Thanks for the reply.

Yeah the Cold Start Valve has been checked by the garage and they are confident that it needs replaced (at their mercy I’m afraid - I’d like to have tested it myself).

The engine was from another 635 of the same year - simple plug and play. Nothing had to be modified.

I’m just wondering if the fuel pump has packed in because I used to be able to hear it prime but now there’s nothing.

Also, they’ve not refitted the air filter and housing (they just wanted to run the car first but it obviously didn’t want to go). I’m assuming that won’t make any difference but does the air filter and housing NEED to be fitted to start?

Thanks again. J
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jps635
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Re: Wont start after engine replacement

Post by jps635 »

Presuming the replacement engine is a known runner is more likely an engine electronic issue - sensor/input. Check it has spark. Check the crank position and speed reference sensors haven't been crossed over at the plugs on the manifold stay - easy to do.

The cold start valve wouldn't in itself stop the engine starting but would make more difficult to start when cold - requiring more cranking. All it does is richen the mixture on starting. Pumping the gas pedal when starting would overcome this.
'85 635csi JPS (RA2-66)
weejangus
Posts: 19
Joined: Fri Apr 05, 2019 6:47 pm
Location: Scotland

Re: Wont start after engine replacement

Post by weejangus »

Engine was running well before being removed from the other car. Has good compression and sounds healthy when turning over.

Thanks for your reply. I suspected that the cold start valve alone wouldn’t prevent the car from starting. I’ll pop down and see the guys at the garage tomorrow and try swapping over the connectors (are they the ones towards the front of the engine bay?).

Failing that, I’ll see if they want to remove the fuel pump and test it on the bench.

Will keep you updated!

J
beemerguru
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Re: Wont start after engine replacement

Post by beemerguru »

Wouoldn't it be easier to remove the gas line from the fuel rail and see if anything is pumping out? Only takes a couple seconds to see if there' s pressure.

And clamp a timing light on a plug lead to see if there's spark

Fire extinguisher handy please.
Greg Hutchinson

'84 633CSi with 478K miles
'81 Euro 635CSi needing assembly

www.airheadadventure.com
weejangus
Posts: 19
Joined: Fri Apr 05, 2019 6:47 pm
Location: Scotland

Re: Wont start after engine replacement

Post by weejangus »

Hi All,

Just to update the thread - I know its been a month or so!

Right, I spoke to the garage owner, he's a big BMW fan and knows his stuff. He put my mind at rest and assured me a new Cold Start Valve would resolve the problem. He said it wasn't just a bad valve, but it was leaking fuel quite significantly and therefore not enough pressure for the injectors - I hope that made sense!

So, the new Cold start valve arrived last week along with new fuel line, seal, etc. I handed it all in to the garage.

Got a call about 10 minutes ago to say the engine is "running like a sweetie" - his words!

Excited is an understatement. I've wanted a 635 for about 30 years after my dad had one in the 80's. When I finally bought this one, it died after about 20 minutes driving.

So, I'm on my way down to see the old girl running. They have a few small jobs to tidy up so I'll get it back early next week and start getting the cosmetics sorted!

Thanks again for everyone's comments and suggestions. Look forward to many more posts in the future!

Jay
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635sharknose
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Re: Wont start after engine replacement

Post by 635sharknose »

Good news! Thansk for sharing.
Enjoy your 635!
Paul
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1987 635CSi Bronzitbeige
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