Bean Posted August 30, 2012 Report Share Posted August 30, 2012 When I parked my 89' this past winter it had started to overboost and cut out while at a rally-x. Once I realised what it was doing I basically drove home and parked it since I didn't have the time or the place to work on it. Getting it sorted now I figured I would test the different components and make sure the lines were intact. Wastegate seems OK with light pressure and suction (whatever I can do with my mouth!), the lines to and from the electrovalve were good, and the electrovalve worked properly with 12V across the terminals. I ensured the wastegate actuator rod could move, and all seemed OK. The connection at the electrovalve was a bit dodgy so I redid the connectors and cleaned it all up. Reassembled it all and the damn thing still bucks and feels like it's over boosting. The wiring has been hacked on the car as I was worried that the overboost sensor wasn't working as it should, so while looking at it it finally dawned on me that it looks like a previous owner has used the overboost sensor to trigger the cold start injector? Wires are cut and soldered all over the place and it's a complete mess - but from what I can tell this is what has been done. I'll recheck and confirm as it was pretty late when I realized what they had done. Still baffled with the overboost as the electrovalve's home position (no power) should basically connect the compressor outlet to the wastegate. The only thing I can think of was that either the wastegate actuator leaks at higher boost levels, or one of the boost lines is. All the lines tested good, and all of the connections are zip tied... This one has me baffled! I'll update later when I can actually use a pressure signal to test all the lines and the wastegate manually with at least 15 psi... Rabin Quote Link to comment Share on other sites More sharing options...
Bean Posted August 30, 2012 Author Report Share Posted August 30, 2012 I should mention that I know how dangerous overboosting can be to our motors - first thing I did after realizing it wasn't fixed was to check the coolant reservoir for bubbles... No bubbles thankfully, but there's still an unknown coolant leak that I've yet to find the source. I may have to look at completely cleaning the engine, then using a dye in the cooling system to see if I can clearly find where the source is. Rabin Quote Link to comment Share on other sites More sharing options...
andrethx Posted August 30, 2012 Report Share Posted August 30, 2012 The wiring has been hacked on the car as I was worried that the overboost sensor wasn't working as it should, so while looking at it it finally dawned on me that it looks like a previous owner has used the overboost sensor to trigger the cold start injector? why would someone do that? was this a misguided attempt at getting more power? andré Quote Link to comment Share on other sites More sharing options...
Bean Posted August 30, 2012 Author Report Share Posted August 30, 2012 Running a boost switch to engage the cold start used to be a ghetto way to get extra fuel on boost, but using the overboost (if that's what they did) is even worse since it's too late to add fuel if the overboost circuit is actually being triggered. All I know is that the wires to the boost solenoid have been spliced, and it looks like it's tapping into the cold start, and there's a relay. Initially I just wrote it off as a starter relay mod when I first found the relay - but last night I was trying to diagnose why it wasn't cutting ignition until 1500 rpm before resuming again and when I traced wires it dawned on me that that's what it looks like they did. Car feels like it's overboosting - then it bucks pretty hard, and resumes as soon as you cut throttle. I really should be running a boost gauge as well - but I'll sort out the boost issue first. I also need to diagnose why the build in boost gauge isn't working. I couldn't find the boost gauge sensor last night... Rabin Quote Link to comment Share on other sites More sharing options...
N9TE Posted August 30, 2012 Report Share Posted August 30, 2012 On overboost the boost gauge will go into the red and you'll get fuel cut. In addition to my blown headgasket, I'm suffering from the same condition as you. I disconnected the electrovalve and it's boosting much like a N9TE. It's derivable now, but still will overboost if I floor it under load. It only overboosted a couple of times for only a few seconds total. Whether or not that caused the blown headgasket - we'll never know. I'm fairly certain that the turbo needs to be redone. That will get done when I do the HG. Quote Link to comment Share on other sites More sharing options...
Bean Posted August 30, 2012 Author Report Share Posted August 30, 2012 My turbo was supposed to be a new N9TEA unit that August installed fairly recent to my purchase - so still pretty new. (I can't confirm with it in place to ensure it's got the .48 AR exhaust housing when it's in place though.) It certainly looks like it with the condition of the wastegate canister and the linkage anyway. With my non-functioning boost gauge - I wonder if that needs to be part of the circuit to ensure the overboost protection is functioning... Unplugging the electrovalve should make it work like an N9TE according to how it functioned. I'll need to spend some more time with diagnosing - but the electrovalve's home position would allow the wastegate to function directly unplugged. So while running it vents the signal and cycles the closure to direct the signal to the wastegate to control the boost curve. If I have to remove the turbo - then I'll likely install the T3/T4 assembly I have into the .48 exhaust housing as it's currently using the .36 AR housing as a stop gap measure. Rabin Quote Link to comment Share on other sites More sharing options...
JunktionFET Posted August 31, 2012 Report Share Posted August 31, 2012 What's kinda funny about about the cold start injector trick is that on the N9Txx it won't work as intended unless the aux air device is open as well. The cold start injector mixes fuel in the aux air device's plenum, and without air flowing through that, the fuel will just pool up and more-or-less drain into the cylinders once the plenum fills up. Quote Link to comment Share on other sites More sharing options...
Bean Posted August 31, 2012 Author Report Share Posted August 31, 2012 That's funny - I never gave it any thought past how useless it would be to trigger it with the overboost circuit as it's already too late, but you're absolutely right as there won't be any air flow and no way for even a venturi effect to bring the fuel out. The engine builds boost nice and strong, then bucks quite violently, but when I immediately let off it resumes running. At first I thought it was the boost cut - but it should be dropping to 1500 rpm before resuming - at least that's what my 86' did. You don't happen to remember if the boost gauge was part of that protection circuit do you? I have to figure that out as well. Just occurred to me that maybe the bucking I'm experiencing might also be the spark flaming out at higher boost pressures. I'll verify wastegate function first - but I'll definitely need a boost gauge before any more testing - that way if it's above 12-14 pisi I know something's wrong with the boost control for sure without having to buck. Rabin Quote Link to comment Share on other sites More sharing options...
JunktionFET Posted August 31, 2012 Report Share Posted August 31, 2012 It doesn't have to drop to 1500RPM to resume running. As soon as fuel is cut, the boost pressure will plummet, the switch should open, and fuel should resume. It sounds like your overboost switch is bunk. Try disconnecting it and make sure the wires are floating, then drive briefly to see if the issue goes away. If it works, but your boost pressure is indeed normal, I'd replace or just do without the overboost switch. I've seen a handful of cars with defective switches that are too sensitive. On one car, stock boost pressure was enough to slightly trigger the switch... so on full boost (11.5 psi or so), the car would occasionally hiccup and feel a bit hesistant, but not cut out completely. This is actually destructive to the engine since it was effectively leaning out the mixture on full boost. If it doesn't go away, I've seen this happen on one other 505 Turbo and it was due to a clog in the fuel tank. The inside of the tank had turned nasty and partially clogged the inlet. This was an '88 which didn't have the pre-pump. There was sufficient fuel volume at idle and part load, but on full load and full boost the engine would buck and cut out violently from lack of fuel. A new fuel tank and the car hauled balls. The boost gauge is a separate circuit. The overboost protection switch is simply wired into the throttle microswitch circuit. When excessive boost is encountered, it is electrically the same as closing the throttle microswitch, which puts the injection ECU is deceleration mode. Simple but effective. Quote Link to comment Share on other sites More sharing options...
Bean Posted August 31, 2012 Author Report Share Posted August 31, 2012 Awesome info man - thanks! I was immediately thinking overboost - but fuel starvation would make sense. It first happened at a rallycross event, and I assumed it was boost related. Now that everything in the boost control circuit checked out I was a bit stumped as to what would be cutting boost. Everything other than fuel starvation was on the list apparently! I'll throw an new fuel filter on for no other reason than I haven't done that yet, and I'll scope out the tank. I've got an optical medical device from a friend that fixes hospital equipment that has a 36" hose that has controls on it so that you can actually move the end around to look around. I thought I left a rag in my Volvo's intercooler when I started it up and was worried it got sucked in. Stuck this thing in the hose and feed it down into the intercooler and could look inside the tank both ways to make sure it wasn't in there. I've still got a much better list to go through to ensure it's functioning now - so I'll hopefully report back tonight if I'm able to figure it out. I may even tackle fixing the wiring hack job - or at the very least to decipher what the heck they were trying to do. Rabin Quote Link to comment Share on other sites More sharing options...
Bean Posted September 1, 2012 Author Report Share Posted September 1, 2012 OK - Got the fuel filter replaced and it wasn't bad at all (it was pretty light), fuel out of the tank was nice and clean and abundant so didn't think it was a tank issue either. Figured out that the hacked wiring and the relay are using the signal wires from the overboost sensor (red wire was cut and splced to the wire to the relay bypassing harness), and the other signal wire is cut into the throttle switch. The 12V output connected to a few wires - one of which does go to one of the wires to the cold start injector. Not sure what the other wires do that are connected to that same 12V output however as they go back into the harness. (I'm going to take another look and draw it out to be certain.) Didn't get a chance to trace wires to see what the other wires did, but tried to see how it was originally wired so that I could return it to stock with no luck. Dug out the wiring harnesses for the three N9TE's I brought back from Montreal and my plan is to "story board" the harness on some plywood. by unwrapping it labeling it, and basically refurbishing it. I should be able to make one good harness, then install it when I do the motor swap. Ideally I'd love to replace the messy multiple connector rats nest with a nice modern wire block connector, but that would be a time consuming task! For now what ever it's doing was working - so I'm just going to leave it as is once I get it working again. Overboost sensor was working - It bucked again after the fuel filter replacement, so I pulled the wires off the sensor and I heard detonation. Sadly I reattached the wires and the overboost didn't work and it detonated once more! (OUCH!) Car does have Bosch 804 injectors in it (337cc/m ones). (Also found stock 802's (284cc/min), and some 357 (300cc/min) sets on the other motors. The dani motor had some unmarked brown injectors I'll need to figure out what they are) I hope to simulate the boost control with my compressor with the engine running (throttle switch open) so that I can see if it's working properly with the electrovalve holding pressure at 12 psi. I know how weak these pistons are for detonation - so the last thing I want to do is to overboost again. I won't attempt boost until I actually find something wrong and it's fixed. Found the boost gauge unit, but I couldn't find the spare one I know I have. Cleaned it up and put it back in but still no gauge function. I'll have to see if I can find how to test it for functionality to make sure it's the sensor - or if it's a wiring or gauge issue. Only other thing I did was to put some Irontite leak sealer into the rad and took the car for a long run to see if it could stop the external coolant leak. I'm not usually a fan of "bottle" fixes - but I simply don't have time to pull it apart to figure out what the leak is. I'd rather put that effort into a proper engine rebuild and swap it in with the new harness. Rabin Quote Link to comment Share on other sites More sharing options...
JunktionFET Posted September 1, 2012 Report Share Posted September 1, 2012 Do you have a test boost gauge in your toolbox? I made one a long time ago using a fuel pressure gauge (0-60psi) and a length of vinyl tubing with a vacuum tee. It was possible to snake the tubing out of a gap between the hood and windshield cowling (there's a small space near the corner that didn't crimp the tube), and into the car via the window. I have two different tee sizes--one for the N9Txx and one for the XD2S/3T. If your car is overboosting, you'll know about it pretty quick. Quote Link to comment Share on other sites More sharing options...
Bean Posted September 1, 2012 Author Report Share Posted September 1, 2012 I had one... Threw it out about 3 weeks ago while purging the garage... It was a cheap princess auto one and I thought I'd replace it a proper one when I installed it. Gonna try and see if any of my turbo buddies have one laying around I can use to diagnose. Initially I was going to do VDO gauges (Boost, EGT, and WB02 AFR) - but likey AEM or Autometer - whatever I can find that does all three. Just off to try to diagnose the boost and to find a piece of plywood big enough to start the harness de-construction. Rabin Quote Link to comment Share on other sites More sharing options...
Bean Posted September 2, 2012 Author Report Share Posted September 2, 2012 Turns out you should never test boost circuit lines using your mouth... Set my compressor to 20 psi and took the hose off at the turbo compressor and let it rip. Hose swelled up and then the rip opened and let the air out! Easiest fix ever. 9/32 wiper/vacuum hose was a perfect fit for the circuit, so replaced both hoses, and used colour coded zip ties as per the book to secure them. Not sure if the hose that was on there swelled, or if 3/8" hose was used - but they were too big. Small hose clamps were used so they wouldn't slip off - but still not ideal. Took it for a spin and the car boosted as usual and all was good... At least I've crossed the fuel filter off the list - but kicking myself for not testing properly and detonating the motor needlessly. Gave the car a quick wash, and pressure washed the underside of the engine and the car to get all the oil and crap off it. If all goes well the Irontite sealer will stop the coolant leak and the engine can remain clean. Thanks very much for the help guys, especially Koll as that topic you posted about proper electrovalve hose routing helped when I put it back together. Rabin Quote Link to comment Share on other sites More sharing options...
billbranch Posted November 19, 2012 Report Share Posted November 19, 2012 Hi, Everybody, I am just getting my wagon back in service. I bought a salvage yard engine for the head (which was good) and whatever goodies I might need. Everything is ready to go, but the boost gauge does not work. Roger remembers it being balky before. He said he has 5+/- volts and vacuum at the sender. Can anyone give any diagnostic tips? I do have decent valves from my old head and maybe other goodies if anyone's interested. Thank you. Bill Quote Link to comment Share on other sites More sharing options...
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