nunnink23

Does anyone know how different a early 90's GM truck TBI is? I would never keep it in my boat, but just for the sake of testing, I am tempted to buy one from a salvage yard and plug it in. I bet it would be cheap. Im pretty sure they run off lower pressure, like 18 or so psi. Not sure if that would be a problem.

I just need to isolate the problem to either the TBI, wiring, or the computer. Even though the computer passed the test at OBD Diagnostics.

BUP

Are you talking about the netrual safty switch here - it should be located in the control box / the shifter or are you talking about the kill switch - have you disable the kill switch - by pass it to see what happens would be my first start. AGAIN THE KILL SWITCH - if you have any inline sealed spark checkers - you can check for spark with them while cranking the engine over - I would look into that either first or second - with the kill switch.

Volvo's do not have an shift interuptor switch just saying

added info if all that checks out good

Cool fuel module here are a problem child with Volvo's. You say you are pumping fuel into a coffee can - where are you taking this fuel sample / pumping location from ?

Map sensor and the reading play a lot for the engine starting and running thru out

MAP Sensor would be my guess here -

Have you tried a portable gas tank with a primer bulb and fuel line on it - hook it to your inlet fuel barb motor side cool fuel side - prime your fuel system with primer bulb and crank engine over then - what happens ?

Did you fill the new fuel water separator completely full of fuel after you change it ? Another reason for portable fuel tank outboard gas tank / primer bulb fuel line set up plus you are taking the boat side fuel supply out of the mix- and this will allow you to prime the fuel system

If this other fuel source is no help with the problem - I would look at MAP sensor and or the COOL FUEL CELL. They have a float in the cell cavity that can get stuck or even have black paint peeled off internally.

When you poored gas down the throttle body did the either of the 2 injectors spray fuel ? How did you test that they were spraying fuel ?

BUP

Have you load tested your battery I can careless about what the volts are with a meter yes that does play a role and 12.7 V is a fully charge battery

Put a solid load on a battery and you could be surprise how fast the volts can drop if the battery has some weak cells or even sulfated plates.,

Are all the connections clean and tight - with the proper cable size and do you have good clean grounds especially back side engine ground (s)

nunnink23

Ah, I meant the neutral safety switch.

In all circumstances the injectors do spray fuel. My subjective opinion is that they do not spray enough fuel, but I truly have nothing to reference this by. They are indeed pulsing fuel however.

The source of the fuel I have been dumping in the engine is the fuel from the tank of my boat. I used the pump to fill up a can, and then used that same can of fuel all day, then every day thereafter to test it.

What is the cool fuel module?

I have a new MAP sensor coming in on Friday. It has not thrown a code for a bad MAP, unless I disconnect it completely, but I am not familiar with how these systems trip codes. I would guess it needs more data than a short 10-15 seconds of cranking (which is pretty long for cranking), in order to set a code.

I have tried a portable tank with fresh fuel, but I did not use a primer bulb. I will try that on Saturday, and drain all the fuel from my fuel cell.

I actually had my fuel cell apart this week because its starting to whine. Sure enough it was full of the black paint residue. I put it back together with o-rings from a kit I have, but I need to take it back apart to put proper Viton o-rings in. I have those ordered already. I will post my final measurements for those o-rings when I am done BTW, since I have gone through a few forums, tried the o-rings everyone else has tried, and I am not happy with how they fit. The float you are referring to does move freely, but again I do not know how to physically test it. Doesn't that float just allow excess pressure to bleed off into the intake? I do have 6psi at the low pressure side, and 30 psi at the TBI, even after I took it apart. Now the fuel cell is nice and quiet, however if I let it sit over night, the fuel cell seems to dry out, since it will whine when I turn it on as if its air locked. That goes away after the first key on of the day. I bet its leaking fuel into the cooling jacket because the o-rings I used are not the best quality, but again, I will resolve that on Saturday.

I never primed the fuel cell BTW. I know that's bad for it. I should do it correctly next time.

I verified the injectors were spraying by observing them with the flame arrestor off.

I would kiss the MAP sensor if that whats causing this. Correct me if I am wrong, but cant you disconnect it and have the ECM go to a default value which would at least allow it to run, although poorly?

Thanks for all the help so far guys.

SB

GM cars/trucks with small blocks have a smaller tbi unit than you do. Your tbi is probably the big block unit with 2" throttle bores.

If you want, I can send you a pair of reman 5.7 (truck/car)to use for testing purposes. Not the same flow rate as yours, but if you are having injector problems, these will let you know.

Send me a PM if interested.

nunnink23

The grounds are clean on the back of the engine, as well as the ones for the distributor and the coil. When I crank the engine the voltage at the injectors drops to mid 10's. Should I measure it at the batteries? They seem really strong. They will crank my engine over all day long without missing a beat. Of course I always put my charger on at the end of the day, or even while I am cranking.

nunnink23

Also, can I ground my injectors manually using something like a test light to see if they spray more fuel than when the ECM grounds them? I would assume the ECM either works or it doesn't with regards to the injector drivers. It has continuity from the injectors to the ECM, and the ECM has continuity to ground... So I might be chasing my tail, but its worth asking.

BUP

Neutral safety switch activated is like you have nothing and the engine will not even crank over - the kill switch / lanyard when pulled cuts out ignition and the motor still will crank over but when working properly - the engine will not start. You still can have very brief engine pop offs with a pulled kill lanyard but a no start condition .

Do you have spark on all 8 cylinders while cranking engine ??

MAP does not have to set a code to be out of range and or bad. Yes it can but - MAP - manifold absolute Pressure sensor - it measures the changes in the intake manifold pressure When the key is turned to the on position MAP is equal to atmospheric pressure. The ECM use this input from the MAP - as an indication of altitude - this is reffered to as BARO. - Barometric pressure

Next the MAP & ECM along with other factors receiving inputs & output - puts this information into voltage. A good MAP will show voltage reading of 1 to 2 Volts max at idle and 4 to 5 volts at full throttle.

BUP

http://www.marineengineparts.com/med...8511_front.jpg

Volvo penta cool fuel cell with the high pressure and low pressure fuel pumps. This pic is the newer style as yours will have a fitting adapter / valve on top of the high pressure fuel pump to check the fuel pressure

Since you rebuilt your motor you had to have this cell off - a lot of gas had to drain out upon removing - and you did not prime this completely with fuel beforehand ??? and you did not fill up the new water sep fuel filter with fuel either. You possible could have a bunch of air in the fuel system and no fuel.

Good luck

nunnink23

I actually did bleed the system now that I think about it though. I took the fuel lines off at the TBI, and bled the supply, then the return. This should have removed most of it. And then I took the filter off, and found it full of fuel.

My kill switch will not allow me to crank the engine. When the kill switch is pulled I cant even turn the ignition on.

I do have spark at all 8 cylinders, I checked with a spark plug tester on each lead.

I am hoping for a miracle with the MAP and ECT sensor. I am pretty stumped.

Do you think I can ground the injectors manually to see if it sprays more fuel than when the ECM grounds it?