Ok I have been searching for a couple hours now but havent found any answers to the first question but figured i would throw a couple out there just cause im asking.

Question 1: I have aluminum heads which requires an adaptor for the temp gauge to fit in the head. Im pretty sure its reading the head temp instead of the water temp. Does anyone have a fix for this? How i come to this conclusion was I have one of those handy dandy infrared laser temp checkers and i point it at the temp sender and its reading what the guage is reading which is anywhere from 220-240ish when hot. I point it at the thermostat housing and its reading about 188-192 and at the radiator and it reads about the same. Now onto the next question.

Question 2: Some JO ran a power wire from the pink wire on the firewall (key on ignition) straight to the fan wiring harness. Im suspecting cause the relay is fried or the other temp sending unit for the fans is not working. I think its under the TB on the intake. Where is the relay? I see 3 on the firewall drivers side. Is it one of them? If so which one? And are there any other ideas for this to be done this way. Oh and when i kick on the a/c the second fan kicks on.

Question 3: Sorry just thought of this while i was typing. Is the second fan only supposed to kick on with the A/C or can it kick on when the temp gets hot enough like the first?

Thanks for the help in advance!!

 

Question #3... The passenger side fan works with a fan switch mouned in the cylinder head and only when the A/C is on and the Temp is at 220 deg.

 

Hmm its my drivers side that kicks on with the A/C and the passenger fan is on all the time. Which is because it was hard wired. Thanks for the info.

 

GM calls the dual fans their "Heavy Duty Fan" system. In this system, the main fan, which I believe is the passenger side, runs on command from the ECM. The ECM recieves coolant temp input from the ECT sensor next to the thermostat housing(yellow wire/ black wire). It uses this information for many things including fuel enrichment. The engine will run very poorly if this sensor fails. When the ECM sees 220 degrees at the ECT sensor, it commands the main fan on. It is common for the fan relay to fail and get bypassed, by someone too lazy to fix it right, with a switch or hardwired to power.

The heavy duty or second fan is operated by a thermal fan switch located in the passenger side head, opposite the temp gauge sending unit. This switch closes at 240 degrees to help cool the engine when it becomes very hot (lower temp switches are available). The heavy duty fan will also run when the AC high pressure switch closes. In this way it serves as the AC condenser fan.

Some of us reprogram our ECMs and rewire the fans to run together as a pair. My fans are programmed come on together at 180 to match my 160 degree thermostat. My engine never gets over 200 degrees.

If one of the fans does not work as described. Start testing at the relays. The fan relays are located, as you thought, by the brake booster. Find a good wiring diagram for your car to use as a guide. Suspect the fan thermal switch if the heavy duty fan doesn't work. Suspect the relay or wiring from the ECM if the main fan doesn't work.

The temp sender is a head temp sensor for a reason. The engineers wanted the driver to be alerted to high head temp due to these engines being designed to run lean.

 

This is great info!!! Thanks!!! Got some questions though. Since I have aluminum heads I have these stupid adaptors for the sensors. My gauge sensor is already off and reading hot so Im gonna assume that the passenger side sensor is gonna do the same thing. Cant really tell at this moment since its broken off. Is there another place I can put it or any ideas on getting rid of the adaptors??

Next question. I grounded the green/white wire with a test light and the drivers fan come on. So that tells me the relay is good since i didnt have to bypass it. Did the same with the grey wire on the other relay and the passenger side came on. This tells me that I may have a temp sensor problem correct? Just want to make sure my thinking is on the right track.

One more thing. What are these? They were hangin behind my a/c compressor.

 

The factory heads have 3/8" pipe thread(I'm pretty sure?) holes for the thermal fan switch and the temp sender. They may be 1/4" pipe but I'm thinking 3/8". My Trick Flow Twisted Wedge aluminum heads have the same size holes. Yours are obviously a different size. However, as long as the thermistor at the tip of the sender and switch make contact with coolant, they should work fine. I have had issues with various aftermarket senders producing low or high readings. I have datastream from my DFI controller to tell me what actual coolant temp is at the ECT sensor, so I don't sweat my gauge reading a little different. I know what hot is and can use the gauge as a reference. Which is about all it's good for anyway.

I'm rechecking what you said about your fan operation and the wire colors you give in your last post. The green/white wire is from the ECM to the main fan relay. So, if the driver's fan is coming on with the green white wire grounded, that means the driver's fan is the main fan. The main fan is not connected to the AC from the factory so that must be something that was done aftermarket. The gray wire is the grounding signal to the heavy duty fan relay. It should be connected to the thermal fan switch and to the AC high pressure switch.

Try to figure out what was done to the fan wiring. The green/ white wire should go to the ECM, connector C3, terminal E8. I'm going to bet that it's been cut and rerouted to the A/C pressure switch or to the AC control head. Put it back the way it's supposed to be. Then rewire the passenger side(heavy duty) fan to the A/C pressure switch and to the thermal fan switch which you'll need to replace. I'm almost sure that wiring diagrams for the fans is available on this site. Try a search to find it.

If you want to lower engine operating temp slightly without reprogramming the ECM, you can switch to a lower temp thermal switch. They are available as a Vette part in various temps. I would suggest 200 degrees and switch to a 180 thermostat to go with your aftermarket heads. But even if you just restore the factory fan system you'll be better off than you are now.

 

https://www.thirdgen.org/forums/cool...ans-arent.html

ASE DOC, I was reading the above thread and my fans are setup as described. My temp gauge sender im pretty sure is the older style. Which on this car would make sense about it reading to high. So Im gonna replace all 3 sensors since i know the drivers side is not correct and the pass side is broke off and not connected. The one under the intake I figure I might as well since i have to drain the coolant anyway Couldnt hurt. Ill take pics of the adaptors. With as much stuff as ive found rigged it may not even need them. lol. The way the fan was wired up was one wire was ran from the harness at the firewall (pink Key on Power wire) to the pass fan and spliced in there. All the wiring for everything else seems to be intact Just some incorrect sensors being used and broken sensors not even hooked up anymore. Mostly though Vacuum lines were a big issue since they decided to rerun a few things. Got them all straightened out though.

 

That is an excellent article. I was forgetting the relationship between the AC and the ECM on the dual fan cars after 87. You may be fine, since the main fan runs with the AC on, that means that the ECM must be able to activate the relay. You can always warm the engine up and be sure it comes on at about 220. You already have the solution figured out for the heavy duty fan.

 

My TFS alum heads have the common old school head 1/2" NPT threads and with a 1/2" -3/8" reducer for the gauge sender, my temp gauge reads almost identical to the CTS reading

 

Here are some pics of my sensors. Notice the older style end on the drivers side and the broken sensor on the pass side. And yes its kinda greasy and grimey. Just got the car a little over a week ago and Still trying to sort the issues out. Then ill do some major cleaning.

 

Here are a couple crappy engine pics. Still trying to figure out how to make the nos look decent and Wireloom everything to make it look somewhat factory.

 

Looks like a fun car. It appears that the heads are drilled and tapped to 1/2" pipe and you have 1/2" to 3/8" bushings installed. This isn't uncommon and I've had to setup gauge senders this way before. It generally works fairly well and as I said, the gauge is only a reference anyway. If your gauge seems to read high, it could be that your head temps are actually a little high. Think about checking your fuel trims and timing. I don't know what's been done with your engine management system to support the supercharger and nitrous. Too often I see these installed with piggyback controllers. The trouble is when you combine two systems this way, they tend to conflict with each other. It's much safer and more effective to install a programmable ECM with boost and nitrous retard functions, and fuel map, that you can fine tune for your application.

 

Ok A little History and parts list.

Now you have to remember I didnt set this up so Im trying to straighten everything out to work together. I have all the paperwork on the 383 engine and it was built specifically for boosted applications. You know blower dished pistons and cam and all forged internals studded everything yada yada yada. ECM is stock as far as i can tell. Still has the blue memcal in it. I am however running a MSD 6BTM ignition and accell coil with a timing retard switch. Bigger TPI runners and fuel rails and injectors with adjustable FPR. THe NOS was an afterthought from the PO who frankly just threw it on there hence the wiring disaster that came with it. I really just want to get it running well like it is cause I think with this application my best solution is to switch it over to ODBII or just go aftermarket FI period. But fundage is tight right now so thats not gonna happen till next year. As far as the temp gauge Ive done the same thing before as well but if you use the sensor with the bigger base alot of times it wont have enough water running around it to pickup a good reading.Been my experience anyway. But as you said its just a reference but i would prefer it be closer to the truth than it is. lol. Aluminum heads are new to me though so they may be different. Always ran cast ones till now. Anyway soon as i get a few bucks together im gonna buy the setup from moats to try and tune the computer I have for now but i know the car will never reach its full potential with it. Besides Itll be plenty enough to play with all the little pony's around here. Oh and the timing was off when i got it as well. The PO kept telling me that the gray connector at the coil was the one that needed disconnecting to set the timing and i ploitely said uh no its this one over by the Passenger firewall but he kept insisting so i just agreed and then when i got it running the other night i reset the timing to 6 with the right connector disconnected and it ran way better. still think it needs more though so im gonna bump it to about 8 then ten and see how it responds. ITs got methanol/water injection also but it needs a new pump. Thatll help my timing a bit also.

 

Yes, the water injection helps alot with detonation by cooling the combustion chambers slightly. The MSD with timing retard helps you dial in the correct amount of timing under boost but it's still a piggyback unit. I like MSD's ignition products but in an application like yours, you want to really have your entire system under one controller than you can tune for the engine as built. For this you want an aftermarket control system. A factory OBDII PCM will not have boost or nitrous retard capability and comes with lots of other headaches. Your best bet would be someting like the ACCEL gen7 or the Holley 950 Commander. Both of these have boost and Nitrous retard maps built in that you can tune to your needs. They both also have wide band O2 sensors which make their fuel maps easy to tune.

EDIT: I forgot to mention Megasquirt. They also offer programmable EFI systems that can be tailored to fit any application.

 

Ok then I have questions!! Again. Sorry.

I am a newbie to fuel injection so bear with me. Can I buy one of these to hookup to my current setup or do I just need to go with a whole new setup like HSR intake and matching throttle body or miniram or accell etc etc etc. What does something like this cost? Ill more than likely need to run a completely new harness to everything correct or do these tie into all my existing stuff. Its ok to talk to me like im 4 i dont mind. LOL

My brother sent me this (http://www.fuelairspark.com/Products...on'-0.aspx) and it was way pricey if i remember correctly. Im in agreement with the piggy back stuff but on my budget right now its gonna have to do till i can get some fundage going. First of the year i ought to be in better shape. Dr. bills suck!! LOL

 

Found these.
http://www.summitracing.com/parts/HLY-550-601/
http://www.summitracing.com/parts/HLY-554-114/
http://www.summitracing.com/parts/FST-301000/

Looks like they will all require new harness's which shouldnt be to difficult to wire in. Pretty sure the original ecu and body harness's are mostly seperate from what i can remember. Maybe replace the O2 sensors with wideband while im at it.

 

Start a new question about your setup and tune in the Turbo / Supercharger dept.this one has answered your orginal question
https://www.thirdgen.org/forums/power-adder/

Plenty out there using stock GM ECM's to run their boosted EFI cars instead of buying a expensive aftermarket setup

Some use the stock 7749 ECM from the boosted Syclone on their 90 -92 cars
https://www.thirdgen.org/forums/powe...9-syclone.html
https://www.thirdgen.org/1990conversion

Some use different factory programming on your stock '730 TPI ECM and a MAP sensor designed for boost ( 2 bar )
https://www.thirdgen.org/forums/post...76-post17.html

 

Will do. Just went out to the car and cut the rigged power wire going to the pass fan (Think they did that cause the sensor in the pass head broke off) and ran it to see if the CTS in the intake was in fact working and it appears it is since the drivers fan came on. So i figured Id jumper the two relays for the fans together by jumping one signal wire to the other so now I have both fans again that run whenever one or the others relay is activated. Simple enough im sure its been done before but figured id throw it out there for posterity. Thanks for all the help and hope i keep getting it on the computer stuff. I greatly appreciate it!!

 

Any of the aftermarket EFI controllers can be used to operate the TPI system. Most aftermarket systems are speed density which simply means removing the MAF sensor and installing a MAP sensor. vetteoz is correct that any programmable ECM can be used also. However, they will not have any function for nitrous retard control. You will end up with a piggy back controller of some kind for that function. Thta's why I recommend one of the aftermanrket systems aince they are designed with high performance engines in mind and have built in maps for managing both boost and nitrous retard. It's not that the stock ECMs can't be modified to do this but they aren't designed for it.

EFI is a strange new world for an old school mechanic but if you can grasp electrical and are willing to do some learning, you will find that it's really pretty straight forward.

 

Boy I never though me and old school mechanic would ever happen but i guess it has!! Bad thing is im only 37. lol but carbs is what i grew up working on. Been doing this since i was about 5 in my uncles shop and on from there. Guess its time to get with the times and update!!! LOL

 

I started on carbs and breaker points ignitions as a kid working with my dad. As the 70s came on, the simple straight forward systems of earlier years disappeared. Replaced by miles of vacuum lines and all manner of devices in an effort to meet emissions standards and maintain some level of drivability. When I started learning EFI in 83, I was actually relieved to see the miles of vacuum lines going away.

Now, I've been working professionally and continually training as a diagnostic technician since 90, achieving master status in 2005. For me, electronic controls have proven much more reliable and easy to diagnose than vacuum controls. It's funny. Right this minute I have a gorgeous restored 57 International Harvester A100 pick up sitting in my bay. Talk about simple. I've also got a 95 Chevy Lumina MPV sitting across from it. Can anyone say can of gas and a match?

 

My driver side fan isn't working, i swapped out the motor yesterday but nothing happened, so there's either a relay on the driver's side of the firewall or that black and yellow wired sensor by the thermostat that causes that fan to not turn on? Also how can i get the fan to go on at a lower temp? i seen you said the engine can run poorly if the sensor fails, does poorly mean after it hits 220 in stop & go traffic the idle can get sloppy/shaky & Cause the car to stall out or misfire when throttling? thanks for all the info, you are a REALLY big help!

 

The ECT sensor can cause issues like these. So can injectors or ICM suffering heat related failure. The main fan is controlled by the ECM. To make it come on at a lower temp you need to reprogram the ECM. The heavy duty fan is run by the fan temp switch in the passenger side head. To make it come on earlier, you need to change to a lower temp switch.

To diagnose a heat related problem, you really want to watch ECM data and look for PIDs that are out of whack when the problem occurs.

 

ASE,
Do you know if the stock fand switch in the pass head is a 3/8 NPT or 1/2?
Looking to do the "total fan makeover" listed in the tech articles and I would like to install the Hayden switch in the block and not in the radiator.

Thanks