Another no start issue

[dsw99a]

Hello folks, hoping someone can point me toward a solution for a no start issue.

Car started as a stock 1978 U.S. 530i. I have since swapped in a m30b34 engine still using Jetronic and also put in a 5spd.

Everything went well got it running, got it re-registered and saftied, started acting up on the way home. Kept running albeit hard starts, which eventually lead to no start. Ive done loads in the meantime thinking i would get it taken care of.

So, im getting fuel (added inline pressure gauge) and ive verified spark (inliine spark tester). Ive reset timing a couple times. Still nothing. Im not getting a cough a backfire or anything but a nice healthy spin of the starter. ive pushed fuel into the intake-nothing. i just installed new wires have new plugs yet to be installed.

Stumped. help

[dsw99a]

bump.

e12Looking for advice.

What are the next 2 things you would check for if you had fuel and spark and a no start on 1978 e12 530i?

[528i-1981]

How are you pushing fuel into the intake? I was going to suggest running a diagnostic on the cold-start circuit. I would pull out the cold start valve and look for a nice spray of fuel when cranking. I suspect that might be the culprit because usually you can get a little stumbling just based on that fuel if you have spark. If this is how you're pushing fuel into the intake, then disregard. If you're introducing liquid gasoline, a spray is far more effective.

If you get a stumble and you have fuel pressure at the rail, then I would suspect the injector circuit.

[dsw99a]

I used a vacuum line into the intake, while i sprayed a very flammable spray (brake cleaner-I think, it made quite a fireball when tested) into the intake while cranking the ignition. I have removed my cold start valve. It was starting pretty reliably before it mysteriously stopped.

[528i-1981]

A low-cost thing to try is the coolant temp sensor (the two-wire one, not the sender to the gauge). Without the cold start valve, it's hard to know for sure, but if the temp sensor is failed-open, it will always think the engine is cold and that could explain the rough running and stalling. The no-start might be because it thinks it's 30 below zero and there's no cold-start valve for enrichment. Just a thought.

[John in the Glade]

What spark plugs did you use?
The modern iridium or platinum plugs will work for a few hours and then fail.
As a reminder, the electrical spark has higher current and needs a solid core conductor such as copper. Sadly, they don’t make the silver core anymore.
Just a thought - check the plugs.

[dsw99a]

Hello folks, still have the issue but i have some new information.
Oh i do have the appropriate spark plugs, they are expensive and hard to find. i dont recall the part#.
I will try the coolant temp sensor if this new info doesnt help me.

I am thinking that my fuel injectors are not firing off. I went to check the injector resistor pack
and 2 of the wires that go to the injectors are open loop. I managed to get the pack off and the resistor looks
old and used but nothing unheard of? Would having two injectors offline lead to a no start issue?
Is there a way to bypass the resistors for starting?

thx.