B230E not passing above 3000Rev in test drive

Duck · 2025-10-31T01:58:27+00:00

So finally coming to the end of my rest efforts on my 82 240 Having gotten it out for a test drive I've found that bizarrely it's unable to climb above 3000...

jamesinc

Can you expand on how you set the test up? Like you had the pumps running and lifted the air metering flap to start injector flow, but nothing came out?

Duck

jamesinc ah I had just stuck the injector into a bottle and cranked it over, so I want to be lifting the air metering plate? I'll take the air boot off and give that a try

Duck

@ramrod jamesinc ahh I see now. It does indeed inject fuel when I lift that plate with pumps running. Even tugging it lightly would inject fuel, so my thought is then would the flow plate not be lifting when the engine is cranking?

ramrod

Duck

The pumps have to be running for an injector flow test.

Join fuses 5 & 7 to run the pumps using an alligator clip wire.

Then remove the bellows to lift the metering plate. Should be able to hear the injectors then.

Duck

@ramrod @jamesinc now a thought I am having is that if it's not injecting fuel when cranking it must be that air is somehow getting past the flow plate. Thus the flow plate is not being lifted and injecting fuel

The air boot between k-jet and throttle body I'm convinced MUST be the issue because it's split in one spot, past me had used a healthy dose of silicon seal to seal it and wrote it off in my head as "fixed"

but I suspect that while it MAY have worked for a while that I should have just replaced the thing (although they are rather pricey) . (in hindsight I feel stupid for not thinking of this in the first place) seeing in practice how the injectors react with that flow plate I can't think of anything else.

What I'll do is tear off the silicon seal, duct tape the split, Then try again and see if the engine will crank over. If it does then I suspect this might have been my issue the whole time…

jamesinc

Yeah, when you crank it should be lifting enough to start the injectors. If you lifted it with your hand no problem, but it won't do it by itself, the most likely cause is a vac leak!

Duck

jamesinc sure enough. Wrapped that sucker in duct tape and it fired up no issues. Wonder if it'll even drive properly now. One way to find out… test drive time

jamesinc

Happy days!

If you're interested in replacing it, GCP are having a sale on at the moment: https://www.gcp.se/en_usd/products/1357088

I think I have a spare used one too, send me a DM if you're interested.

Duck

jamesinc ah yehp I'll take a look it'll definitely be worth replacing.

-edit-

Shipping is a bit youch but I've paid worse for less before, so given that it'll be a fresh airboot in my hands I'll put the order through for it.

Cheers James!

Duck

@jamesinc @ramrod alright so test drive result. It was that damn airboot for sure (curses to past me for assuming it wasn't going to come back and bite me.)

it's hard to say what the mixture is looking like and if there could still be vacuum leaks, however, I could floor it into kickdown and it'd Rev past 3000 which is IMMEDIATELY an improvement…

jamesinc

It's not too hard to hunt down vac leaks. You just need some start ya bastard, or some brake cleaner. Idle the car and just hit all the joints and see if the idle picks up. Around the injectors and their seats is a common source of vac leaks.

It's very unlikely the mixture itself will need adjustment, only once you have eliminated all vac leaks and any other running issues would you consider messing with the base mixture. It's a finely-tuned adjustment too, it's not really possible to calibrate it without an exhaust CO meter providing feedback.

Duck

jamesinc aye, will give it a whirl once the weather is a bit sunnier over here, one of my buddies has been looking at fashioning an exhaust tester for tuning too so will be able to get a better picture in time.

Thinking as well of a good addition I've been wanting to add to the car (that the same buddy suggested) is bolting an 02 sensor into the exhaust with a gauge.

Feel a bit daft for not thinking about the airboot. that being said though having to test stuff on the k-jet was a good lesson has definitely expanded my understanding of the system.

ramrod

It’s ALWAYS

The little things that cause the biggest effect.

Duck

@ramrod @jamesinc so had a good bit of difficulty getting it started this morning, pulled the boot off and tugged the flow plate a little to get some fuel in the chamber, and it started up quite snappily (might investigate cold start Injector)

Did spray some brake cleaner around the big leaking points to no obvious effect which seems to speak well that we may be "mostly" free of vacuum leaks, I'll be more confident once the fresh boot arrives

Now interestingly, investigating if the starting difficulty could be related to the system not holding pressure overnight I've come across something that seems unusual to me.

I understand that the accumulator is responsible for holding the residual pressure in the system, so I went to have a look for it and… couldn't find one? Neither on the brace with the fuel pump where it should be for this year, and not on the fuel tank like older year models any thoughts on that one? It seems like a fairly important piece in the whole k-jet system so it's absence strikes me as a bit unusual.

jamesinc

That's weird! You will be able to see with your fuel pressure tester if you have an issue, if the pressure is fluctuating rapidly then it could cause problems.

But I think unless you are seeing wild rapid pressure fluctuations (needle is a blur and fluctuating more than a few psi), look at your cold start injector first, run the pumps and see if it drips, and check the spray pattern is not a jet of fuel. The cold start injector only runs for a couple seconds when you start cranking so blink and you will miss it.

Duck

jamesinc think I got our culprit, no injection from the cold start injector when cranking, checking voltage at the plug when cranking (meter set to 20V) read 0.08volts

What is the voltage meant to be at that plug James? Can't immediately find information regarding what it should be and the greenbook just mentions is there voltage

Edit

I stand corrected instead of going across the pins on the plug I went from the positive pin to an earth on the engine to ground and got about 8.6ish volts flactuating a fair bit so that's a rough estimate, but around 8 volts at least

Next test we're gonna hotwire that injector and see if we can't get it to inject

Conditions for the test was with the CPR, air aux valve and ignition control unit unplugged, from what I understood of the testing process from the greenbook

Duck

@jamesinc nah. did not react to the hotwire not a peep from it does seem like cold start injector is kaput

jamesinc

It should be 12V when cranking + cold

I don't think there is an online copy of the K-Jet operating principles manual, here are some excerpts that I think will help. This is from the 1977/78 manual for a B21E, but your B230E setup is very similar, I think they just added the constant idle system and moved the fuel filter from the firewall to under the car.

Image description

Anthony

If you need the big rubber boot I have a few in good order up in the rafters. Message me if interested.

Your certainly learning all about mechanical FI.

The No.1 culprit if having issues is the CPR -control pressure regulator. If your tech minded you can check a few fundamentals but its a miniature mechanical instrument inside. Thing is the unit controls pressure both cold, gradually warming and hot running via a hot finger leverage. So a very important unit to be spot on spec.

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