924Board.org

[Chaos]

Cool. Thanks, eddie.

Definitely the direction(s) I've been headed in. I've been flushing the injectors with techron. Exactly the same procedure you've described. After flushing through about 80oz of highly-techron-ed fuel, I've still got one with a questionable (seems to be oscillating?!?) spray pattern, and the one other one still leaks a bit.

I think, for starters, I'll replace those two injectors. Then I'll replace the other two when money is a little less tight.

In the meantime, I'm most concerned with that one bad insert. I haven't a clue where to get a replacement for it.

As for the WUR, I've cleaned it out a bit. Plan to blow out the lines with compressed air today or tomorrow. Resistance is checking out ok, but obviously need to get a pressure gauge on it to see what's really cookin'. I've already been all over that one thread you linked, but there is some real solid literature over there at that ferrari400 site, so definitely thanks for that one.

The last bits of vacuum hose I need to replace are the ones that connect near the back (firewall side) of the intake manifold, the one that connects to the engine under the timing belt tensioner, and finally the one that runs between the TB and DITC. Now that I've got the WUR out, that one in the back will be easier, but still a pain in the ass, and I guess on the front side, I'll have to take the AFM all the way out, which I didn't really want to do, but... meh. I've got most of next week off. Wish me luck!
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'81 US 931 "Rochelle"

[Fasteddie313]

[Chaos]

Oh yeah, yeah. No, sorry about that. I knew exactly what you meant... I actually replaced the recirc valve rubber (on both ends) about a year ago, and while I plan to double-check 'em, they're not what I was referring to.

There's a (16mm ID) hose that connects literally just below the timing belt tensioner, and runs over to a venturi connector that joins into the (~22mm ID) hose going between the inlet of the AOS and somewhere behind the manifold, roughly right under the WUR.

It's probably worth mentioning that my car doesn't have the breather adapter update like most of the 931s I've seen pics of. I'm fairly certain that this front-side connection under the tensioner would be the bottom connection of that breather adapter, if I had it.


In other news, I spoke briefly with John over at SpecialTAuto yesterday and he asked me some questions about what's up with my car. He sounded pretty darn convinced that my problem is a malfunctioning frequency valve, which he said he can clean for me for $35. Apparently most of the DeLoreans are 81s, as well, and they're all having that same issue right about now. He says he's cleaning 1-2 of those each day, lately!


Either way, I've got some new injectors on the way, and I'm going to wait and test my pressures before I send John anything, in case the WUR needs a rebuild, too... might as well do them together.
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'81 US 931 "Rochelle"

[Chaos]

So I just removed that hose from over by the tensioner. Seems like I could've been more accurate before... it turns out it's clamped onto a small pipe back there, not straight into some random-ass port directly on the engine. (guess that explains why I couldn't seem to locate it in the PET. haha!)

Now that the hose is out, I can tell it doesn't seem 100% stock to me. I'm thinking this was something some PO put in there. But, that's not the weird part.

Weird part is that there's some strange goop inside the hose at this end (the end where the venturi connection is seems pretty normal - tiny bit of oil, nothing else). I have no idea what this stuff is, but it's pretty impressively gross.
I posted some pics and description over here if anyone wants to look and maybe help me figure it out: https://imgur.com/a/dG4Ir
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'81 US 931 "Rochelle"

[Fasteddie313]

I wonder if someone tried one of those magic engine cleaning products that you let your engine eat from the intake, and a lot of it ran down there and had no where else to go..

that stuff may also be gumming up your recirculating valve..
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80 Turbo - Slightly Modified

[Chaos]

Heh. That'd be a hell of a thing.
Can't remember if I've actually opened up the recirc valve since this whole issue began, but I think I opened it to at least check on the gaskets on both end-caps.
I'll take a look at it soon, just to be sure.
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'81 US 931 "Rochelle"

[Chaos]

It's been a while so I figure it's time for a quick update:

In the past couple of weeks when it hasn't been freezing or raining, I've gotten 2 injectors, one injector insert, and that breather hose replaced, and I also sent my frequency valve to John at SpecialT to have it cleaned, which came back looking great.

When I got everything back together and tried to run her, she started up without too much fuss, but the idle was noticeably high and took its time to settle back down when I revved the throttle. Pretty obviously running lean/got a leak somewhere... which I quickly determined was the hose connection at the bottom of the AFM, which had recently pulled out. The JB that I used to reattach it didn't do me any favors at all. So, I popped it back off, cleaned it, and reattached with Red RTV this time. I can't say I'm fond of how that feels at the moment, but it's definitely sealed up that leak.

Now she'll fire up when cold and doesn't slowly bog down and die while warming up, like before. So I'm 99% sure that having the FV cleaned was a huge help. But... she does still die after warm-up. This time, I decided not to mess with the mixture at all during it, and just observe while she ran. Since I was paying more attention and not trying to "fix" it the whole time (aka - making things worse for the next restart), I could clearly see it went like this:

Starting from cold, fires up on ~1st or 2nd attempt - idles a little high but not terrible - relatively smooth, but slightly stumbly, all through warm-up - rad fan kicks on... insta-death: RPMs suddenly drop real low, very suddenly. Basically impossible to keep running. Essentially goes from running alright to acting super-rich.

Second time I tested this, I tried carefully playing with things when it got to the insta-death phase and it turns out: More fuel = die faster. More air = die microscopically slower.

I've watched it happen twice now and it appears to be directly related to the fan kicking in.

So, I'm wondering if I've got weak spark issues complicating things, and I'm going to try to poke at that later today. I'll probably finally get around to adding the extra ground strap from manifold to the chassis, over by the battery.

In other, more exciting news, I've finally got all my parts for my CIS tester and I'm hoping to get that plumbed in this weekend. I've also just ordered a cheap smoke tester setup because I'm too lazy to gather stuff up and build one. So, hopefully by this time next week, I'll be well on my way to actually knowing what's going on instead of randomly poking it with sticks and scratching my head.
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'81 US 931 "Rochelle"

[Chaos]

On my lunch break today, I finished getting my fuel pressure tester plumbed in and only had time to run a quick cold test with the fuel pumps jumpered and injectors still in. (yeah, yeah - as soon as I came back inside I realized that I should've pulled those first. )

Anyway - System pressure appears to be within spec. Good deal. Seemed to be sitting right around ~88-90 psi.

Then it got interesting- I closed the valve to check control pressure. The needle dropped.. and then shot right back to where it was, ~88 psi. *womp womp*

I had the WUR out a couple of weeks ago and blew out the lines and cleaned the screen on it, so I'm going to go ahead and say it's a safe bet that it's just the WUR and not clogged lines.

If there are any other tests you guys suggest I run before I send this thing out, I'd love to hear 'em!
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'81 US 931 "Rochelle"

[Chaos]

Ok so long story short, my WUR has been replaced.

Car fired right up after getting everything back together and felt great however, as I was trying to dial in the mixture with the frequency valve/duty meter tactic, she seemed to start bogging down again, slowly, but surely. Definitely not behaving properly. Duty meter was reading in the 70s/80s again, just as before, too.

I've since gone back through and done further CIS testing, and everything is looking perfect, except for my warm control pressure. it's a little low. 3.0-3.2 bar, every time.

My current theory is that my return fuel line has a blockage. That would explain why the frequency valve is trying to lean things out, while the engine slowly bogs and dies as if it's running rich, right? - not enough fuel getting sent back to the tank, so as it builds up, it just flows more and more into the cylinders until she just can't keep it together any more. Does this sound right or am i theorizing outta my ass?
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'81 US 931 "Rochelle"

[Fasteddie313]

[Fasteddie313]

[Chaos]

oh yeah. definitely a typo. my mistake. and the pressure tester is configured correctly, but thanks for double-checking.

injectors aren't spraying with the plate at rest. i'm good to go, there.

Here's what i'm getting:

System: ~6.1 bar
Cold Control: ~1.6 bar (it's been pretty cold lately. 50F, max)
Warm Control: ~3.0 bar, which it comes up to fairly quickly. Can't be more than a minute or two.

Also, I found the post I was thinking of when I mentioned a restricted return line earlier:

http://www.924board.org/viewtopic.php?t=35734

[Fasteddie313]

[Chaos]

whew, yeah. that's a lot to think about. this might take a few reads to fully internalize. haha

but in the meantime, just to answer your questions/concerns - the WUR was rebuilt by John at SpecialTAuto. CIS systems are pretty much the bread and butter of his business and exactly what he works on day in and day out. several members of the board swear by him and his work. i'm pretty confident he knows his stuff, but to your point, yeah, it'll definitely be worth a call to him this week to discuss. i'm sure he'll have some decent insight for me, either way.

as for the control pressures, i know that my cold control appears to be under spec, but there are a couple of extenuating circumstances to consider -
first, oddly enough, my WUR is from an S1 931, not an S2. don't ask me why. that's just what's in there. as a result, that's what i sent john and that's what he sent back. an -062, not an -091.
second, the cold pressure spec is always written as "@ 20C" which would be perfectly fine, if i were in a climate controlled area and that was the ambient temp i tested at.

long story short, i don't think the control pressure reference graphs i've seen go down far enough to actually show what pressure you should see at ~4C, which is what i'm currently testing at. considering that the cold pressure for an S1 is 2.0-2.4 @20C, i'd be surprised if 1.6 bar was way out of spec for an ambient temp that's lower by 16 degrees.

either way, at this point, this is all temporarily moot because everything went to shit this afternoon when i tried running her around the block while still warming up, and i rather suddenly lost the ability to shift gears. (yay)

shifting from 1st gear to 2nd, heard a pop from the back of the car (like something breaking, not an afterfire), and never managed to get into 2nd. just revs and revs with no power to the wheels no matter where the shifter is. and yet, now she doesn't want to start back up, either, as if there's an extra load keeping the starter from turning. naturally, this all happened as it was getting colder and darker outside and i wasn't about to mess with it right away. *sigh*
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'81 US 931 "Rochelle"