Manifold pressure reference outlet

I see in some of the pics and comments posted here that the Manifold pressure reference outlet has a check valve, can anyone tell me how the check valve works. I have a massive overfueling problem, when I disconnect the MAP sensor it has no effect nor does the ECU throw out an error message. Need some help

Is it a check valve, or moisture filter?

I've never been sure myself

It's a restrictor and possibly a water trap / filter. It takes out any large pulsations, and protects the expensive MAP sensor from inlet backfires. I have never cut one apart, so am guessing there's a filter within... It's most definitely *NOT* a one way valve, that'd never work...

Its got copper gauze/wire wool inside it

Thanks, now we know, cheers!

Thanks Guys, thats what I thot, no check valve just a filter. But there is a photo on this site which says with check valve. Which I cud not understand. Thanks. Now I will have to start new thread in regard to my over fueling issues.

Back to my original post, when i disconnect the MAP sensor my ECU does not record an error message. should it?

On a stock TT if you pull the electrical connector off the MAP sensor the engine should run badly, and it should put the MIL light on and record a fault code. Not sure about just pulling the vac / pressure hose. This assumes stock ecu. If you pull the hose off at the MAP sensor nipple it pulling vacuum with the engine idling? We need to see if this is pneumatic or electrical.

Hi Chris. The engine is already running badly I have massive overfueling to the point of oil contamination. the engine runs rough, struggles to rev. will not idle. if i pull off the injector plugs while running the revs increase and the engine smooths out a bit. tried this on all injectors same result. checked the ECT sensor values ok, checked voltage to MAP sensor.

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Hi Chris. The engine is already running badly I have massive overfueling to the point of oil contamination. the engine runs rough, struggles to rev. will not idle. if i pull off the injector plugs while running the revs increase and the engine smooths out a bit. tried this on all injectors same result. checked the ECT sensor values ok, checked voltage to MAP sensor.

I still don't know if this is a stock car, with a stock ecu, or what? And are you *REALLY* in Swaziland???

The car is stock jspec supra TT 1993. Stock ECU with power house amuse chipset. perhaps I shud start at the beginning, car had an engine bay fire due to a loose battery burning thru fuel line to aftermarket FPR. All hoses, vacuum lines, rubber parts on LHS of engine were destroyed. Engine Bay Wiring harness, fuse box, Igniter, ABS, Air conditioning all burned. Engine harness also destroyed. I sourced spares from Keron @ Extreme Performance. Replaced the following, Engine Wiring harness, Engine Bay Wiring Harness, Oil Pressure switch, knock sensors,Camshaft position sensors,MAP sensor. Throttle Body and all sensors. Can send you pic was a real mess. Following the repairs car started immediately, but sounded like it had no power, Struggled to raise revs and when it did poured black smoke from exhaust, was overfueling. After a dozen or so cold starts the engine oil was badly contamiated with petrol. Have drained and replaced. But have not eatblished the cause. Have checked ECT Sensor appears to be ok giving correct resistance, checked voltage to MAP also ok.. ECU not giving an error message. Tried unplugging TPS and Sub TPS. ECU shows open circuit, Likewise with the ECT shows open circuit, but when i disconnect the MAP sensor nothing. When I remove any injector plug while running the engine improves. The replacement harness appeared to be from an automatic supra, the air con and the ABS units have not been replaced. Not sure where to go from here and any advice would be greatly appreciated. Yes I am *REALLY* from Swaziland, and because of this I am *REALLY* in S%#T I have no access to special tools or equipment.

I'll help as and when I can, my favourite dog and best doggie pal is dying, and I am trying to make his last days as fun as possible. Plus I am mega busy with work.

Answer me this, does the MIL (engine warning light) work when the ignition is turned on? Do you have a multimeter and know basically how to use it? Have you got a mechanical (with a tube to it) boost gauge, or can you get one? Given this gear I can perhaps help you track down your issues. But DO NOT keep running it, over fuelling of that level can do serious engine damage quite quickly.

Finally have you got access to a spare, known good ecu? I had a MKIV TT in a few years back that had an ECU with some daughter board upgrade and it did just as you describe. I checked all wiring and sensors and finally found the ECU itself was knackered.

One quick thought, there are two wires with 6mm eyelet terminals, they are the ECU grounds and attach from the engine loom to the underside of the inlet manifold. They are black wires. If they are not bolted to engine ground on a good clean bit of bare metal, the ecu will not function correctly, and nor will the MIL light work. It's easy to not see them and not bolt them up, I see it regularly and have been guilty of forgetting them myself. If there's no MIL light find them, there's a photo in the forum somewhere, maybe from member DavidP, showing their original location

If all else fails ask a witch doctor

I'll help as and when I can, my favourite dog and best doggie pal is dying, and I am trying to make his last days as fun as possible. Plus I am mega busy with work.

 

Answer me this, does the MIL (engine warning light) work when the ignition is turned on? Do you have a multimeter and know basically how to use it? Have you got a mechanical (with a tube to it) boost gauge, or can you get one? Given this gear I can perhaps help you track down your issues. But DO NOT keep running it, over fuelling of that level can do serious engine damage quite quickly.

 

Finally have you got access to a spare, known good ecu? I had a MKIV TT in a few years back that had an ECU with some daughter board upgrade and it did just as you describe. I checked all wiring and sensors and finally found the ECU itself was knackered.

 

One quick thought, there are two wires with 6mm eyelet terminals, they are the ECU grounds and attach from the engine loom to the underside of the inlet manifold. They are black wires. If they are not bolted to engine ground on a good clean bit of bare metal, the ecu will not function correctly, and nor will the MIL light work. It's easy to not see them and not bolt them up, I see it regularly and have been guilty of forgetting them myself. If there's no MIL light find them, there's a photo in the forum somewhere, maybe from member DavidP, showing their original location

 

If all else fails ask a witch doctor

Yes the MIL Light works, I can read error messages from the ECU as mentioned. I do have a multimeter and know basically how to use it. I do have a mechanical boost gauge although not reconnected yet. No I do not have access to another ECU but have had the car since 2010 with no issues until the fire, not sure if any possible short in the burnt wiring harness cud have caused damage to the ECU. So it looks like I will have to follow the same route you have mentioned checking wires and sensors. Then if need be try and order an ECU from Keron. perhaps some injectors as well. The grounds you mention for the ECU are in place to a good clean ground. I have not driven the car only started and stopped after trying different things the car has not been driven. I am aware of the possible damage from overfueling. Can I email you a couple of pics to give you an idea of what we are dealing with here. Sorry to hear about your best doggie pal.

Sure, my e-mail is [email protected]

Basically over fuelling, assuming a sound ECU could most likely be an open to the coolant temp sensor (the two wire one), or no MAP sensor signal to the ECU, or a shorted map sensor or sensor loom.

MAP sensor has three wires. An ecu ground, a 5V reference signal from the ECU, and the signal as a voltage FROM the MAP sensor *TO* the ecu. If you can carefully probe the *ECU* connector that goes to the MAP sensor signal connector, with it still connected to the ECU, you should see varying volts if you suck and blow on a length of hose connected to the sensor nipple. Have you got the wiring diagrams? The wire FROM the sensor to the ECU is yellow with a black stripe. (Or black with a yellow stripe, depending how you look at it). Measure the voltage between that terminal, still connected to the ECU, at the ECU itself, with red lead of meter to the yellow / black wire, and the black lead to a good clean chassis ground near the ECU. Should be less than 5V and vary with blowing / sucking on the pipe. Ignition on, engine not running.

Have you got access to various resistors?

The air temp sensor in the inlet manifold will also skew fuelling, but I doubt it would make that much difference, I haven't actually tried unplugging it to present an open sensor fault.

Also see if there's vacuum at the nipple of the Sputnik filter on the manifold that feeds the MAP sensor. Use your boost gauge for this on a piece of hose, something like screen washer hose.

Detailed photos of good quality of the MAP sensor plumbing would be good. Have fun! I would expect disconnecting the MAP sensor plug to present a fault code if done with engine running. Same with coolant temp sensor and air temp sensor, have you got the list of fault codes?

Thanks for the kind words re the dog!

Is the car a manual or an auto? I may have a known good ECU, but would need to check if it's an auto or manual one. I would have to ask good money for it as I use it as a spare for testing, but if you get really stuck....

The car is jspec, 1993 Supra 2JZ GTE, with 6 spd manual box, though now has harness from an auto car. On the other stuff, the ECT Sensor I checked the resistance was spot on 1.6Kohms @ 30*C. When I disconnect while running the ECU throws up open circuit error message. On the MAP sensor I tested it earlier and got 5v supply from ECU and 2.4v to ECU at atmospheric. Will try the suck blow test today and see that the voltage varies. The Plumbing, will send pic, but its right according to what I see here. On the Sputnik Filter I never tested for vacuum but I could blow through in both directions before installing, so it is not blocked. Have not checked the Air Inlet Temp sensor as yet. Trying to avoid running car. The resistors I am not sure will have to check around local electrical shops. What would we need and what are we gonna test using them. The ECU will see how we progress.....I was offered one by Keron when I bought the other stuff, but decided to wait and see. Edit - Tried the suck blow test you mentioned on the MAP sensor -atmospheric 2.4v, sucking 2,2v, blowing 3.0v. No idea what pressure or vacuum, but the voltage does fluctuate.

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It's a restrictor and possibly a water trap / filter. It takes out any large pulsations, and protects the expensive MAP sensor from inlet backfires. I have never cut one apart, so am guessing there's a filter within... It's most definitely *NOT* a one way valve, that'd never work...

Hey. Thanks for this.

Bump

Check the MAP signals at the ecu connector. Check for vacuum at the fuel pressure regulator valve. Check fuel pressure. Get injectors flow tested. Try another ECU

Hi Chris. Please check my last post on the map sensor, Vacuum at the FPR is OK. Fuel pressure I can adjust. before all this happened I was running 3.5 bar fuel pressure, but now if I raise the fuel pressure the car does not want to start because of the overfueling, If I lower the fuel pressure to 1 Bar the car actually runs better, but this again is related to the over fueling problem. I do not have access to another ECU. Trying to rule out all other possibles before trying to purchase one from UK only to find I still have the same problem.

Basically this could take you a LONG time. You need to check continuity and correct signal voltage levels against those in the shop manual *AT THE ECU* connector, with it plugged into the ECU and the ignition powered on. Also check the throttle position sensor. Again, this has a 5V reference voltage supplied to it *FROM* the ECU, and it also has an ECU sourced ground. Finally it gives a control voltage out back into the ECU as the throttle is opened and closed. These tests take a long time, but once all sensors are PROVEN to be talking correctly to the ECU, the engine has fuel regulated at the correct pressure referenced to plenum vacuum / pressure levels, and the injectors are being pulsed correctly and have correct flow rates and are not sticking open , you are left with the probability the ECU is faulty. Given the extent of the fire damage I trust all the engine looms were changed, and all the sensors themselves?

There's no real trick to diagnosing this, just extreme levels of patience and being methodical and taking notes as you go. I myself might be tempted to try your ECU in another similar car, but I appreciate given your location this is probably not feasible. I wish I could think of a magic solution, but it's the sort of job you can do 2at home", in fact paying someone like myself could cost a fortune. I might find the problem in ten minutes, it might take days.

Raven had a similar problem on his TT transplant I think it turn out to be injector wiring to be bad ,

but as you have had an engine fire the ecu could be goosed as i expect everything was sorting out as the wiring insulation would have been melting . As Chris says your going to have to check each wire .

its a real shame you cant just try another ecu. could save you alot of trouble can you not buy one try if its the same sell it ?

All the looms were replaced, as were all the fire damaged sensors. I appreciate that this could take some time. All I am asking is will you continue to help guide me through it, as you have already done.

Yes, of course, but now you must dive in and check. Another thought, post me the ECU and I'll try it on another car?

*VERY* very slim chance the issue is a blockage in the air intake system, but I would think that unlikely. Check air filter, air filter to intake trunking, make sure the turbos aren't seized so they won't turn. Even a seized solid turbo would probably allow a stable idle, it wouldn't pass enough intake air for high RPM correct operation though. Unlikely scenarios, just another idea.