Mr.Monsoon

I have a 85 12A turbo sand rail that will easily rev past 7500 in neutral. Under load it gets to 4500 and starts to hesitate, run choppy, lose power, etc. If I work the throttle, I can get 5200ish out of it, but no more. Eariler this year it would hit 6500 no problem.

The plugs seem fine, it has a brand new fuel filter (2 10 min runs), new fuel lines, very recent Weber carb rebuild, replaced vacuum lines, fuel pressure is set between 3-4 psi, gas tank is full.. There is no cat converter, no air flow sensors, etc. its pretty basic. It seems like my problems begin when the turbo tries to kick in, but i could be wrong.

I've looked up other threads similar to this, but none of the other vehicles quite match my profile. Any help would be appreciated, thanks.

diabolical1

iTrader: (3)

what turbo?
is it blow-through or draw-through?

i'm a person that actually believes in coincidences, but this is not one of the times i think it applies. this is where i would start.

other ideas ...

is it a hard set 3-4 psi or do you have a rising-rate regulator?

have you double- and triple-checked the integrity of the intake tract (no leaks)?

Mr.Monsoon

I just want to say, this forum bugs the heck out of me. It logs me off quickly, randomly goes to a white screens, and doesn't record my replies, just says, sorry, you need to log in before you post a response, and loses the messages I type, even after I logged in 10 mins ago. With that said, lots of helpful info.

I have a blow through system, Garrett turbo (I think its off a boat from research), hits 10-12 psi (on the random occasion car runs).
Fuel regulator is set at 3-4 idl, drops to 2ish for s steady throttle, will spike up to 4ish with sudden throttle input, will spike even higher when turbo hits. When system blows off pressure will drop to 1 for a split second, then rises again. I have a brass T coming off my intake mani, one line runs from my fuel regulator to the intake mani T, and another line runs from a HKS valve on top of the Intercooled Turbo manifold on my carb, to the intake mani T. I think it influences fuel pressure.

I can always recheck for leaks, none found so far.

I just want this to run. I have had it 7 months, and it has ran correctly for literally 1 hour, and then the idle died, and it has never run properly since. Sadly, no shops within a 2 hr. radius know anything about rotaries.

diabolical1

iTrader: (3)

check your cookies settings.

yes, that sounds like the reference line for the regulator.

you said it ran good for an hour and then died, what exactly happened (circumstances) also, was it acting like this BEFORE the Weber rebuild?

i guess someone may as well be the bad guy and say it, so here goes. check the compression.

Mr.Monsoon

It died after an hour of running. Was idling down a small hill and it died. Essentially, it wouldn't stay running unless I kept it above 1500 rpm. This was BEFORE the carb cleaning and rebuild. Upon rebuilding I found bits of black stuff in the carb jets, and a broken off tip of an idle jet stuck in its seat. Also rejetted for elevation, 145 mains and 180 air correctors.

I tired to do a comp check but it has decided to not start today. Maybe tomorrow.

diabolical1

iTrader: (3)

whatever came just before this part is probably what's really relevant. were you running the hell out of it for the other 59 minutes - and if so, how was it behaving then?

what kind of Weber is it and what size?

Mr.Monsoon

Because of the area, there was alot of sub 2000 rpm driving, when we were abel to open it up it was for 5-6 seconds, rpms never past 7k.

I'm running a weber IDF40. My plugs (if it matters are dark brown, almost black on the plug face. I'm using a 100:1 mix ratio, non synthetic.

diabolical1

iTrader: (3)

finally, some tangible, useful information. an IDF ... and it's a 40? my immediate thoughts are you simply have a bad foundation.

from what i understand, the IDAs are notoriously bitchy when it comes to boost (as compared to the DCOs which seem to be more amicable), so i will go out on a limb and propose that maybe the IDFs share that trait as well.

maybe the black stuff you saw clogging the jets were pieces of your floats?

off-boost, i think the carbie is simply too small for your application.

Mr.Monsoon

Still makes no sense as to why it WAS running..... anyhow I do have a IDF44 I could put on, think I might as well give it a shot?

diabolical1

iTrader: (3)

but it does make sense. if you meter a fuel and air mixture into an engine it's going to try to run - without any regard to whether or not it runs correctly. i'd be willing to bet that if you had had some sort of AFR monitoring in place, you'd have seen some pretty interesting things.