SpeedOfLife

iTrader: (16)

The car I looked at Sunday ('87 TII w/ 86,000 miles) has [hot start issues]. We replaced the starter and it fired right up and ran real well except that it had an idle problem until it had run for about 5 minutes. You had to hold the gas to keep it from dying and there the idle would pulse from 1000 to 1250 RPMs a couple times each second. So after it ran for a little while it held an idle fine, but then we couldn't start it after shutting it down (and a few minutes of cooldown idling). We checked the compression with a standard gauge from the trailing (upper) plug holes and got about 70-70-70 on the rear and 65-65-70 on the front (I JUST called the guy who helped me check it and he said he didn't hold the accelerator down, meaning the throttle body wasn't wide open to get plenty of air in there). We suspected flooding, but the trailing plugs were pretty much dry so we checked one of the leading plugs and it was slightly moist, possibly enough to just be from oil. However I do understand that if it's flooding then a compression reading will be low, plus, I have a precedent with the last car I looked at which I'm certain wasn't burning all its fuel, some guy botched a compression check and got 70 front and 30 rear, but the buyer got 90's all around I believe, so that makes me hopeful that this car I'm getting actually has good compression.

Until this week the car sat for several months in a heated garage and the oil tank had been boiled and coated before it was stored and all the injectors are very new, so I'm a little concerned. What can you guys tell me about that? Did I get a decent compression reading and the motor needs new seals, is it flooding only slightly, or is there some other reason it won't hot-start? I was told that if it was flooding the plugs should be wet, but maybe it doesn't take much at all and our understanding of 'wet' was actually 'soaked', and what we observed was in fact 'wet'. I do plan on buying this car this week, I just want to research this as much as possible.

I'm very excited btw! Hopefully I can pick up the car this week!

Additionally, the battery is pretty new, but still might not have turned the motor at the full 250 RPM, and I wonder if the pulsing was due to a bad PD.

VacavilleFC

70-70-70, 65-65-70, motors toast, no compressions,

RotaryEvolution

iTrader: (30)

numbers do seem low and can cause hot start issues.

SpeedOfLife

iTrader: (16)

The car runs fine it just doesn't hot start; it boosts, it pulls, but it also seems to be flooding either due to poor compression or something else. Again, flooding can CAUSE poor compression readings, so poor compression may not be the problem, and on top of that, the guy turning the key didn't open the throttle (by mashing the gas pedal). Also, I already stated pretty much EVERYTHING in this post in my initial post.

I'd appreciate some opinions from those more thorough and informed.

edit: I'm not being rude to Karack, his post wasn't there when I went to write this post.

RotaryEvolution

iTrader: (30)

what is your problem douchebag...

opening the throttle may net you a ~5 PSI difference, having a fully charged battery and good cranking starter is where you might see any real differences in compression so if you want to be as thorough as you claim to want to be then get a cranking figure, you should be cranking close to 300RPMs or higher during the test with both leading plugs out while 1 is being tested, netting at least a 80PSI figure for each face for a total of 3 pulses on each rotor being consistent, even a dip to 65 on one face can be your cause of hot start issues with a tiny chip in a seal.

before you attack anyone you should know how these engines operate. low compression does NOT mean the car will run with any real less of a degree of performance once it is running, you hardly will notice low cranking issues at all while driving around town. low compression across the board will ONLY really affect cranking.

if you want to bypass your flooding theory then simply get the car running and shut it down, it cannot simply flood itself until at least having tried to crank it over drawing in too much fuel, before cranking it do your warm engine compression test.

now if you want to continue to be an *** then that's fine but you really should check who you are going to be an *** to beforehand next time. no wonder i don't come to this sub forum any ******* more!

SpeedOfLife

iTrader: (16)

I wasn't insulting you, your post wasn't there when I went to write that post. I know you've been here a long time.

RotaryEvolution

iTrader: (30)

well VacavilleFC is probably on the right track, those numbers do sound a bit too low even if flooding and no throttle input was in the equation.

mileage isn't always an indicator of engine life as it could have been abused it's whole time in service and the engine could just be very tired.

SpeedOfLife

iTrader: (16)

Yeah, I do understand that if not well maintained it can go downhill much faster, and I do know that two owners ago it was certainly neglected, the guys I'm getting it from were just trying to get it back into shape.

When I go to pick up the car I'll put some oil through the chambers then run it a little and then do another warm compression check. Does that sound like the 'best' course of action?

RotaryEvolution

iTrader: (30)

that's all you really can do, but a carburetor cleaner/water/atf treatment certainly wouldn't hurt and might massage some sticky seals into giving you some better numbers, same with dropping a little 2 stroke oil into the tank and premixing for a little while(even with a functional OMP)

SpeedOfLife

iTrader: (16)

ok awesome, I'll try all that. except the atf, I've heard way too many accounts of it eating the oil seals. I have heard about water treatment, but I want to get it home before I try to loosen the carbon deposits in case it makes a seal stick, which I really hope it doesn't...

I got a can of sea foam in preparation for something like this, has anyone had experience(s) with sea foam and how did you get the best results (putting it in the gas or chambers or some other way?)?

edit: also, I know the FSM says 85 psi is the low end for operation, but I know motors have run with significantly lower compression. what I'd like to know is what kind of compression people might have gotten soon before blowing their motor (excluding extreme conditions and highly modified rotaries). it'd be nice to fix most of the issues this summer and work on rebuilding this winter or later because then I should finally have a garage to work in and more time by then to save up for a seal sets.

RotaryEvolution

iTrader: (30)

i've seen people with numbers in the 60's able to still start and drive the car but at that point they probably needed a fuel pump kill switch to get it to fire up. anything even remotely lower than that probably would require a buffer like 2 stroke oil or MMO in the chamber to help aid compression to get a motor to turn over.

SpeedOfLife

iTrader: (16)

Ok
so if compression doesn't affect how it drives once it's started, which I've heard before and I assume it's true, what does compression tell about the reliability of the motor under driving stresses?

RotaryEvolution

iTrader: (30)

not a whole lot, just that things are wearing and compression likely will continue dropping at that point until the motor is just impossible to start, how quick is hard to guess.

most motors that die do it in a split second, aka blown apex seals due to faulty tuning, inadequate care of the engine and fuel system or irons/coolant seal failures which are unrelated to compression.

SpeedOfLife

iTrader: (16)

Ok, that's good to know. I do realize I will probably need to rebuild soon, so I'll be saving up for that, however I'm hopeful that since it's apparent no seals have blown the housings and rotors will be reusable, as well as the turbo.

I drove it home today, about 50 miles mostly highway. The idle issue nailed me once before getting to the highway, but after a roll start we were on our way. Aside from that, it ran fine with reasonable power except it would stutter very frequently even without making much change in throttle adjustments.

I'd like to at least get some autocross out of it this summer, and I won't be doing much for performance mods, so does anyone have any idea if this would be ok to do? The last thing I want to do is blow the motor, I'd like to keep it in good shape for when I can rebuild it, but I also don't want it to sit for the first few months I own it, I want it to LIVE AGAIN.

NoDOHC

Some recomendations:

Burp the coolant system:
An air bubble may cause the water temperature sensor to get an inaccurate reading.

Install a fuel cut switch (easiest place to wire in is the relay above the brake pedal.)

Do like Karack says and premix.

Change oil to 20w50 (who knows what is in there now.)

Experiment with a new battery (helps cranking speed.)

Experiment with flooring vs. not flooring vs. flooring for a little while.

Do injector leakdown test.

I don't know if all or any of these will help, but the coolant bubble turned out to be my problem (hot restarts, but it wasn't flooding, it was too lean.)

The fuel cut switch may even save you money on insurance (an anti-theft system), no I am not kidding here.

Syonyk

Also, you might want to dig up a copy of the FSM and test the thermosensor - as I said when we were picking it up, a bad thermosensor that tells the ECU the engine is cold can cause hotstart flooding.

http://www.rotaryresurrection.com/2n...nflooding.html at the end of the page.

I'd agree, the cranking speed seemed a bit low. With low compression, you need every bit of help you can get while cranking. Also check the grounds/starter connections/etc.


-=Russ=-

SpeedOfLife

iTrader: (16)

That's a good summary plus good additions. The coolant sensor HAS been a tad testy Sunday and yesterday when we first started it, and I mentioned it may need to be burped.
I will be doing a full 60k tuneup asap, so of course the oil change will be included. One thing I disliked was they used a FRAM oil filter the last change... The oil on the dipstick WAS quite fresh and clean though, still, I'll still do it because you never know.
So when you dealt with that, you're saying you couldn't hot start? I just want to be sure I'm reading it right. Additionally, the plugs were never even very moist, so we were wondering if it's flooding at all, plus, when it died once on the way home, unflooding with the fuel pump relay disconnected didn't get it started, but the first shot on a roll start did.
And I like the idea of theft prevention plus it may come in handy for the other obvious reasons. I will keep the switch hidden, too. And if I could find a way to afford more than liability insurance I'd be thrilled. All that said, a fuel cut switch will probably be one of the first things I do.

Thanks everyone! If you have any more ideas please let me know

harley71105

I'm just glad the KURACK and SpeedOfLife worked things out...they both seem like OK dudes....

SpeedOfLife

iTrader: (16)

I did get it started up during lunch today, it took a few quick fuel pump disconnects then turning it over to get it started, but it worked. Sadly I don't think I'll have time to work on it tonight. Once warm it even held an idle at 1000RPM, but after driving it just a minute it wouldn't hold the idle again. Oh the curiosity!

SpeedOfLife

iTrader: (16)

Turns out my alt was only putting out ~12V, so who knows what problems have just been caused by that. Hopefully things will get much better when I get to install a new one tomorrow. Could low system voltage cause a rough idle and pinging? (yeah, I noticed it's been pinging once it gets warm, most noticeable at low RPM's, but I'm not sure if it's doing it higher up).