tbroadfoot125

Ok, I am new to the site and to posting on the message boards/forums. I have read the forums in the past looking for answers to some of my questions and have found a wealth of knowledge here. I hope I am posting this in the correct section.

I have a 1983 Camaro Z28 in which I transplanted a 1987 305 TPI from a wrecked IROC-Z. I have changed the system over to Speed Density rather then the Mass Air Flow system. I am using a 1227730 ECM with a stock prom ( AXYD 16163139) and a Painless Wiring VATS bypass module #64023. Using the stock 700R4 transmission. Here is my problem that I can’t figure out.

Engine cranks but does not start. Using my noid light, I am getting signal to the injectors (tested all of them). I have good spark. If I spray gas from a spray bottle into the throttle opening, the engine will fire up until the gas runs out. I did a fuel pressure test and when I put the ignition “on”, I have no pressure. When I crank the engine, I only get about 30psi, but as soon as I stop cranking the fuel pressure drops to 0 like a rock. I have used my Auto Xray (model XP240) and the scan results show no trouble codes found.

I back probed the ECM at A11 and E13 but I get no signal for the fuel pump relay when I go ignition “on”. I should get battery voltage for the first 2 seconds. Putting 12 volts to the Fuel pump test connection shows the pump is working but only generates about 30psi. Pump is a Airtex replacement (from Auto Zone) which should (per spec sheet) generate 65 to 95 psi. I have no fuel in the vacuum line for the pressure regulator and a vacuum test shows it holding a vacuum. Tested all wires for an open or short and have found none. New fuel filter, supply line not crossed with return line, no visible kinks or breaks in the lines.

Any suggestions?

G-reg

iTrader: (3)

Sounds like at least two separate problems to me. If it were me I'd be looking at why your fuel pressure drops to zero right away when the pump turns off just because I hate dealing with electrical gremlins I'd block the fuel return line, give the pump power and see what kind of fuel pressure you get and if it drops back to zero right away. It should have really high pressure and it should hold it. If it gets higher fuel pressure and holds it, there's something wrong with your fuel pressure regulator. If it doesn't, its probably something on the fuel pump end, either the pump itself or the hose attached to it in the fuel tank.

For the priming issue.. I'd look at how the VATS delete is wired in. Its getting the crank reference signal off of the distributor and telling the ECU to run the fuel pump when you're trying to start the car, there must be another wire that also provides a signal when the ignition is turned "on" that is not connected or not working. That's just a guess though, I've never looked into getting rid of vats so hopefully someone else can give you better advice!

tbroadfoot125

I'm in the process of pulling the tank out of the car to check the pump and the connections to the pump. Once I am done with that, I'll try blocking the return line and see what happens. I'll post my results with that. Waiting on a reply from painless wiring on how to test the VATS delete module. But from my understanding if it is not working, the car would not crank, but don't qoute me on that information. I'm looking up more information about the VATS. Thank you for the assistance with this problem.

ASE doc

VATS disables injectors only. It has no affect on fuel pump control. When you crank the engine, does the fuel pump power up immediately? If it takes two seconds or so to power up, it may be getting power only through the oil pressure/fuel pump switch. The relay may not be getting the activation signal from the ECM at all. I don't know GM ECMs by number but my diagram for the 91 speed density TPI Z28 shows the fuel pump control signal coming from pin A1, not pin A11. You might want to test at the relay, both for activation signal and for power at pin E with key on and immediately upon cranking. If you're using an aftermarket/generic relay for the fuel pump, output will be pin 87.

tbroadfoot125

I double checked in my schmeatics from a 1991 Camaro Shop manual I bought on Ebay the fuel pump signal is from A11 for the 5.0L and 5.7L engines. The schematics do not show any output from A1. I hope the schematics I am looking at are accurate. I was told by several GM techs that the any of the 90-92 camaro schematics will work.

I am not sure about the pump powering up or taking a few seconds. I can not hear it while cranking the engine. I will have to test at the relay and have someone crank the engine to see if I am getting the signal to the relay or not. After you mentioned it, I don't hear it power up when I turn the ignition "on" but not crank. I don't get that 2 seconds of run time. I'll have to check the circuit and relay to see if I am getting a signal for the fuel pump.

I have the pump out and I did not see anything visible wrong with it, all connections were tight. I am going to try to get the adapters for the fuel pressure gauge and test the output PSI of the pump also. I also plan on plugging the fuel supply and return lines and applying some air pressure to them to see if I have any non-visible leaks in the lines.

ASE doc

Leave it to "Some Data" to have their diagrams out of whack. I rechecked and found the actual ECM connector view and diagram for the 91 Z28. You are correct that the pump command signal is on A11 and the fuel pump monitor is on pin E13. These should both have 12v for 2 seconds when the key is first turned on. If A11 has 12v and nothing on E13, it would point to a problem in the relay power supply, ground circuit, or the relay itself. In my experience the GM relays rarely fail.

If there is no fuel pump command signal at pin A11, it would have to be a loss of ignition on signal from the ign switch to the ECM, which doesn't jive with having injector pulse. Or, the ignition on signal is shorted to BATT+ so that the ECM never sees the key turned to "on". Does the check engine light work as it should? If not, I would start my checks by verifying power on with key on, and off with key off at ECM pin A6. Otherwise, you may just have an ECM with a bad fuel pump driver. Of course, verify that all ECM power and ground circuits are solid.

You still have an issue with fuel pressure and if there was no trouble in the tank, I would first verify a solid 12v and good ground at the fuel pump. Then, go on to testing the regulator by blocking flow back to the tank on the return line as G-reg suggested.

tbroadfoot125

Pulled the pump out of the tank, according to a parts diagram I was missing a isolater that goes between the pump and pulsator, which I had to order. Everything else looked good. As soon as I get the tank back in, I'll check the regulator by blocking the return line as suggested. Replacing the rubber hose connections between the sending unit lines and the steel lines just as procaution while I have the tank down.

I doubled check and I have voltage going to the relay when I place the ignition to the on position. I'll see what happens when I block the return line and go from there. Thanks to all helping me with this

tbroadfoot125

Tank back in and same problem. I disconnected the main feed line and rigged the fuel pressure test gauge to the line. I used battery power and a external 12v power source and connected to the fuel pump test connector. I still only get 28-30 psi at best. Even though the pump "runs", I suspect the pump is bad. Specs on the pump are 65 to 95 psi and suppose to be a direct replacement for the original pump.

As soon as power is disconnected, pressure drops to zero. With the tester on the feed line and the feed line not connected to the fuel rail. I would believe this isolates the problem to be either the line or the pump. I can't find any kinks, tight bends or anything else with the line so It has to be the pump.

Any opinions before I under go the ordeal of taking the tank out again? Thanks again for the help!

DENN_SHAH

iTrader: (1)

if you still have the pulsator, toss it in the trash next time you have the tank out. you should have gotten some high pressure fuel hose and hose clamps with the new fuel pump, use that instead of the pulsator.
the purpose of the pulsator was to help even out fuel pressure and help reduce pump noise. they cause more problems that they are worth.

there should be 2 wires with power at the fuel pump relay.
i don't have my diagram open so i can't give you the pin numbers.
i know one should have power at all times, when the relay is turned on it supplies power to the pump thru the relay.
i don't remember if the power pin that supplies power to turn the relay on has full time power or not. i believe it only has power with the key turned on.
the ground wire from the relay goes to the ECM and is how the ECM controls the fuel pump relay.

ASE doc

With the fuel pressure line isolated, there is no place for the fuel pressure to bleed off, except in the tank. You must be missing something in there. As DENN SHAH says, if the fuel sender still has the plastic housing pulsator between the pump and the metal tube, replace it with hose. It is common for these pulsator units to fail, causing a loss of fuel pressure. You must use high pressure fuel injection hose on any connection in this system.

tbroadfoot125

I pulled the tank out of the car again. I have the pulsator on top of the fuel pump, so I will pulled that off and replace with some high pressure hose. I read a couple threads about this and people say to use SAE J30R10 hose inside the tank. Been looking for it, seems like this stuff is expensive. As far as I can tell, there is nothing missing in the tank. The sending unit is brand new, so I don't think there is any issues there. I'll pull the pulsator and go from there.

I am tempted to drop the sending unit into a bucket of gas, hook the pressure tester to the output and drain back to the bucket just to see what kind of pressure reading I get. However, I am not excited about hooking the power to it will all those gas fumes lingering in the air.

Thanks again to all for the help. This is driving me nuts.

ASE doc

Honestly, I work with fuel and fuel pumps constantly. So far, no explosions. I was going to suggest bench testing the pump and sender for leaks and pressure. Just try to figure out a way to connect power without creating sparks close to the open can of fuel. I know that I would do it at this point if it were me, rather than reinstall it not knowing for sure.

DENN_SHAH

iTrader: (1)

im in the car with doc on testing with the sending unit not in the tank.
i no longer work on cars for a living, but i too have have done more than a few tests like that and also haven't had a fire, yet, and i hope i never do.
when testing it out of the tank, i would expect to see fuel spray from around the pulsator where it pushes on the fuel pump & sending unit.
at the regulated pressure i've even seen brand new pulsators leak like that, which is why i stopped using them before GM issued the TSB.

when possible, i used a connector to plug into the sending unit with a fuse & a switch inline on the power side and i liked to regulate the output pressure. even though i've done it, i have always hated to dead head a fuel pump.

ASE doc

I've always followed the Chrysler dead head test rule of 10 seconds max. I hate to do it too.

tbroadfoot125

I have the pump out of the tank and this is what I tried. Hooked a "T" into the fuel supply line, one end going to a gas can the other going to the pressure gauge. Tested with known 12v and got no pressure on the gauge but the bucket was draining and I could see fuel pumping into the can.

Second, connected the gauge right to the fuel feed and run the test again. The pump went up to 60psi before bogging down at which I disconnected power. Both tests without the pulsator, just a piece of hose.

In the 1st test, without any restriction on output, I am not surprised to see no pressure since this would just be a free flowing system. Sound correct? In the 2nd test, with restriction the pump showed more then enough pressure and I am fairly certain I did not run the pump for more then 10 seconds.

This there another way to connect everyting up outside the tank that I should try before I call the pulsator the culprit and put everything back together without the pulsator?

Thanks again for all the input and advise.

ASE doc

Actually, I would have expected to see more than 60 psi on that pump. I am used to seeing the GM FI pumps run 80-100 on dead head. I suppose that 60 is enough since the system only runs 35-45. I just don't want to dismiss that as a possible issue.

I would say at this point, unless you are willing to replace the pump right now based on the low dead head pressure, the next thing to do would be to install the tank just far enough to run the pump and test pressure with the return line open and closed to see how the regulator is doing. Try applying vacuum to the regulator diaphram to see if it works at all. Now you know that the pump makes 60psi. With the return line closed, you should see 60 psi at the test port. If not, you have a pressure loss somewhere(leaking injector(s)?).

One other thing that I would try would be to disconnect the return line at the rubber section either by the tank or in the engine compartment, place it into a container, and see if the reg is passing fuel below 45psi with no vacuum. Then you know for sure that it's toast.

tbroadfoot125

I'm going to replace the pump since the pressure did not come up to the rated specs of the pump. I'm also going to order some SAE J30R10 hose for the connection between the pump and output tube on the sending unit. As much practice as I have had removing and installing the gas tank, I don't want drop is again unless really needed. It will take a couple days due to the holiday to get the hose. when I get everything together and buttoned back up. I'll get a pressure reading at the fuel rail and I really hope this solves the fuel problem.

Thanks again for all the help and have a happy 4th of july.

DENN_SHAH

iTrader: (1)

i've always used the hose & clamps that comes with the new fuel pump and seldom had any problems with it.

60 is a little on the low side, but if the hose between the pump & sending unit is leaking, then the presure will be low.

ZZ3Astro had problems with the in-tank hose using hose that didn't come with the pump.
post #340
https://www.thirdgen.org/forums/tpi/...garding-7.html

a vid he posted showing what he found,
http://www.youtube.com/watch?v=HuYWc...ailpage#t=188s

if you test as shown in the vid, absolutly no smoking and no fires or other ignition sources anywhere close.

the pulsators leak the same way.

tbroadfoot125

As a test I used hose for fuel injection and high pressure clamps. However, I did not look for leaks around the hose when I was testing. I was watching the pressure gauge rather then the hose. I'll run the test again and see if I have any leakage. I read a few posts about the hose instead of the pulsator and I talked with the guy at my local auto parts. He said "The standard fuel injection hose will work but it is not submersable and will swell and loosen over time". "The gas will cause the outside of the hose to become spongey amd eventually fall apart causing it to leak". "The gas resistent properties of the hose is only on the inside of the hose".

The hose that comes with the in-tank pumps is suppose to be SAE J30R10, rated but according to the local auto parts guy but some of the import hose falls short. Either old pump or new pump, depending on test results, I am going to go with the SAE J30R10 hose. I may have to wait a few extra days for it, but I know I will not be back into the tank because of the hose.

Once I get the hose, I plan on bench testing before I drop it back into the tank. During the bench test, I will pay close attention for any signs of leakage around the hose.

Thanks for the link to the video and the advise.

tbroadfoot125

Ok, got the submersiable hose and put everything back together. Too hot in garage over the weekend to work. I have 43psi at the fuel rail now and the car actually fires up now. When I rev the engine it stalls out, also if I try to go WOT. I thought I might be low on fuel since there is only a couple gallons in the tank from all the times pumping it out to drop the tank. Added more gas and the car fires up but it sets a Code 43 according to my scanner.

The only thing I can find about the Code 43 is that it involves the knock sensor. This code seems to be missing from my reference material. Found a couple post online but each troubleshotting guide was different. Seemed confusing to me. Scan tool did not indicate a knock signal due a capture with the engine running or a monitor an capture data aquisition. It seems like once it fires up all is good then if you push the gas pedal it just dies. Also if you don;t touch the gas and just let it idle it dies after a minute or two. No sputter, just quits.

Going to talk to GM guys to see if I can get a print out of the code 43 troubleshooting. In mean time, any suggestions would be great. You guys were right on the money with the pulsator being the problem.

Thanks again!

tbroadfoot125

Ok, call me crazy but I went out and ran a couple tests on the knock sensor. tested for voltage from the ECM and reconnected the wire. I cleared the code 43 by removing the + battery cable for about 5 minutes. Fired the car up and did a scan with the auto xray. Car ran about 30-45 seconds and just died. Reviewed the data from the scan tool and no trouble codes found but I did see something of interest. According to the scan tool the oil temp is -38.6 (minus 38.6). Its 84 degrees the garage, so either the scan tool is not reading something right (diagnostics pass upon start up of tool) or there is something wrong sensor wise.

My theory is the oil pressure is dropping off and the oil pressure switch is shutting down the engine. I don't have a oil pressure gauge on the instrument cluster just a lamp but it does not do anything. Does anyone have any ideas about this -38.6 degree F, oil temp reading? or what sensor the scan tool would be getting this from?
Thanks

tbroadfoot125

I fixed the intermittant Code 43, which came down to my own mistake of hooking the knock sensor wire to a old temp sensor (which looks just like the knock sensor).

Still fires up, but after 30 seconds to 2 minutes it dies. I have the fuel pressure gauge on and fuel pressure does not drop off, I have a oil pressure guage hooked up, seperate from the one on the back of the engine, and oil pressure does not drop off. Idling, the car will just die and then you can hear the fuel pump. Giving it throttle and the car does the same thing.

Wondering if the oil pressure switch is bad, causing it to think the ooil pressure drops off so it shuts down the engine. It does not sputter, spit or anything, just like you shut the engine off. Anyway to test it, it is the older style with 3 prongs, not the newer 2 prong rounded with a notch connector. Still have not figured out why the scanner shows oil temp at -38.6. Oil has been in engine, not running for a long time so I am thinking of changing it as a precaution. Any thoughts? I would really like to get the car running good before I return to work next week. Thanks again for all the input and your time.

ASE doc

Unless you personally wired in an oil pressure fuel pump cut off switch, loss of oil pressure will not cause the engine, in the 87 TPI to stall. The stall is sounding more like an ignition problem. The ECM doesn't monitor oil temp, only coolant temp. -34 is generally the reading we see with an open sensor circuit. Check the ECT sensor at the front of the intake manifold(yellow wire/black wire) for being disconnected. This sensor being unplugged will cause the engine to run very rich and suffer severe power loss. I have not seen this cause stalling. Connect an inline spark tester to one of the plug wires and watch for spark drop out. This would be caused by a faulty ICM or pick up coil.

tbroadfoot125

I'll have to get a inline spark checker, don't have one. The 87 was updated to a 90 speed density, so it does have a oil pressure switch for the fuel pump. I rigged up the switch and tested it and it was alright and oil pressure doesn't seem to drop off, maybe a little low (50psi).

I am starting to think the ecm is bad. I got the car to run better by turning up the idle at the adjustment screw. Idling at 1200rpm, the car runs smooth and no die out when given throttle. Below 1000-1200rpm, rough idle and acts like it wants to die. I let it run for a while and took some scans with my scan tool just to see what was going on. I was hoping to notice something, out of the ordinary but still not sure. I wrote down the results after each scan so I could look them over. The temp reached over 220 and the fan did not even kick on. I tested the fans with external power and both work. Sometimes it dies and starts right back up, other times you have to let it sit 5-10 minutes.

Are these symptoms a sign of a bad ecm? No codes are set per scan tool. I was thinking that is could also be the ignition control module in the distrib getting hot and acting up. Not sure, going nuts with this project. I am really glad those with a wealth of knowledge are so helpful. Thanks again.

ASE doc

The oil pressure switch is ONLY A BACK UP for the fuel pump relay. It does not prevent the pump from running normally. The ECM controls the pump through the FP relay, regardless of oil pressure and the oil pressure switch. The ECM powers the pump for two seconds for priming, then activates it again when it sees crank reference pulses. The ECM will deactivate the pump only when the crank reference pulses stop. This is absolutely the truth. It is a misunderstanding to think that the oil pressure switch will cut off the fuel pump. This would only happen if the pump was running only on the switch, in the case that the relay or control circuit was faulty. You can verify normal ECM FP relay control by testing for power at the small green and white(DrkGrn/Wht) wire at the relay with the engine cranking or running.

It's important that you understand how the fuel pump control circuit functions so that you don't chase your tail diagnosing a problem.

tbroadfoot125

Thanks for clarifing the oil pressure switch to the fuel pump relationship. That saved me time chasing down a wrong idea of what is wrong. I am not sure what is wrong with the car. I was taking stabs in the dark and looked at the park/neutral switch signal to the ecm based on park neutral "not detected" scan results. I found a broken ground wire. I have a B&M Megashifter, not the stock shifter so I thought something might be wrong there. After fixing, the car fired right up, idled a lot smoother. The 87 uses data from the park neutral signal for the vss diag, egr and idle air. So I figured the 90-92 would use the park neutral data in some way. I guess I was right there.

However, it still fires up runs a little while and then just dies. It dies just like someone turned the ignition key off. No spit, no sputter just dead. I am still suspecting there is something goofy with the ecm since I am not getting a fan on signal to turn the fans on. Ran car, coolant temp 224.8 per scan tool and fans didn't come on and scan tool indicated fan off. If I play with the throttle a bit, it will stay running longer but still dies. Oil pressure ok, fuel pressure ok. Waiting on inline spark checker to come in, had to order one. Would the ignition module cause this problem?

I can't thank everyone who has helped me get this far enough. Thanks again!

ASE doc

This would be a common symptom of ignition failure. Be sure to check out the pick up coil as well. It should test between 800 and 1000 ohms(green and white wires).

tbroadfoot125

Unfortunately my vaction is over. So with my work schedule, I have less time to work on the car. However, I am going to stab in a new distributor since I got some funny readings trying to do a test on the pick up coil. I hope this and a new ECM solves my problems. I want to thank everyone who has helped me run down this problem. Thanks again