I have a TPI setup on a 327 in my 1968 C10. I run the EBL P4 to control the system. It is speed density BTW. Great overall for about 12 years. A month ago, I go out in the morning to start it and it will turn over, but not start. No indications something was bad in the drive before I parked it. When it is cranking, I am getting some of the cylinders firing, the manifolds are heating up and the engine continues to spin for a few seconds after I stop cranking the starter. I have replaced the plugs, cap and rotor. I also swapped ECM's as I have a spare from before I got the EBL and I have the same condition. With key-on the fuel pump pressure up as normal. I see ~40PSI on the fuel rail gauge. It holds there while cranking.
I have the small cap distributor with external MSD coil.

Something seems to be only partly working. What are some of the test procedures I can start with to diagnose this? Does this seem more like a fuel or a spark condition?
Thanks
Ryan

 

Check basics, injector ohm, injector pulse, spark. Could be as simple as a bad icm or shorted injector shutting down the injector driver.

 

Post a in focus, close up picture of the fuel injectors.

 

That is going to take a bit of time to pull them, but I will. I replaced the coil this evening, no change. I am now going through the injector connectors with a noid light. cylinders 1& 3 are flashing, they are the only ones I have tested so far before I ran out of time.

 

Spark was verified?

 

No I don't mean take them out for pictures. As they are installed. To identify them.

 

Ah, I understand. Yes spark verified on all cylinders with an inline test light. Ill get pictures up tomorrow evening. Thanks for your help.

 

I just wanted to make sure your car didn't have the Rochester Products Multec fuel injectors that came in 1989 to 1992 TPI systems and other GM engines.

Those greyish green things are the Devil's work. Their part number should be GM RP 666. The Mark of the Beast.

You don't waste any time troubleshooting these injectors. You identify them and if they have the "Mark of the Beast" you throw them away and replace them with new Delphi replacements of the correct size.

 

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Apologies for the giant image. I was not able to get a look behind the injector to see a part number. I think they are original judging by the rust...

 

Just curious are the plugs wet ? Does it try to start with cranking pedal fully depressed or with a shot of starting fluid ?

 

They aren't RP Multecs so that is good. Something could be wrong with them but they aren't defective by design.

Normal troubleshooting from here on.

 

I verified a few things tonight. All the injectors are pulsing based on the noid light test. I verified the TPS is seeing 0.54 volts during cranking. I have attached a datalog from the WUD from the EBL taken while cranking just in case someone sees something that catches their eye.
I checked a spark plug after cranking and it is slightly wet with gas. Still getting random firing during cranking. Getting spark at the plugs. Something obviously doesn't line up. I am wondering about the fuel pump or fuel pressure regulator. Gauge on the rail hits 40 with key on and then drops until I start cranking. During cranking it stays around 40. Then drops off right away as soon as I start.

 

I tried starting fluid a week ago and it did not start. I would try it again but the can fell off the shelf and broke off the nozzle.... Need to get another. I am going to replace the vacuum line also, I noticed it was hard and slightly cracked at the t junction. Would that impair the fuel pressure regulator to the point of not functioning?
If I step on the peddle fully it pops a bit more but still wont start. I find I can get more popping and firing with the peddle partially depressed but no start. Under no conditions will it start.

 

Edited a few replies.

 

Because the fuel pressure would fall off fairly rapidly after key-on, I tested it via clamping the pressure line immediately after key-on. Pressure would then hold and drop off very rapidly after I let go. I think that is letting me know the check valve is not functioning. I have a replacement coming this Saturday.

 

New Fuel pump did not fix the issue. Pressure still falling off. Fuel pressure regulator next.

 

Do you have a standard ECM you can try? Just to rule out something wrong with the EBL.

 

I do, I did try that at the start of the process and no difference. But for the time it takes I should do it again.

 

No change with a different ECM.

 

So, After a bunch of delays I put on a new fuel pressure regulator. Fuel rail pressure gauge held 40 when I turned the key on and the fuel pump primed. Then, after cranking and failing to start, I noticed that rail pressure is back to not holding after key-on and pump priming.
To re-cap, new fuel pump, new pressure reg, new plugs, new cap, new rotor. Noid light has shown all injector are being triggered. All plugs are being fired based on an inline plug test light. I get popping, so some ignition is occurring, but not enough to catch and run. I also tested resistance on each injector, they were all about 16 ohm*m's.

Given the lack of rail pressure, is it likely I have an injector that is leaking? Would one bad injector though likely cause a no start condition like this though?

 

Almost instant pressure loss at pump off would definitely point towards leaking injectors. Especially with you having replaced all other components that handle the fuel pressure. Might not necessarily be your problem but definitely isn't helping it.

 

Try reading this from General Disorder, smart guy and knows his stuff. His post helped me out when I was chasing my tail about KO and no fuel pressure. First off though, I'd buy a new ICM for the distributor. then throw those injectors out and get a new set, your choice of brand, from Southbay.

https://www.thirdgen.org/forums/tpi/...injectors.html

Keep us posted.

Brian

 

New Injectors coming Monday from SouthBay.

 

Nice, that'll solve that problem. I shoulda mentioned I'm running a EBL Flash 2 on mine and never a problem related to the ECM. Still, it doesn't hurt to run everything down.

 

Ryan, your voltage it too low. Either your battery is going bad and can no longer hold a charge, or your alternator simply isn't charging it properly and it needs to be replaced. I just looked at your datalog. Hook your laptop up again and bring it to the WUD screen. Crank the engine again and watch these two specific areas; Ignition Voltage on the far left, and your RPM in the center of your screen on the gauge. Notice how during cranking your voltage is dropping down to 10.0 V, and your RPM never exceeds 200-RPM during cranking. The pump is not being triggered/pulsed by the ECM to fire because the ECM is not seeing 400-RPM, which is when it is programmed to trigger. As for the sudden drop in fuel pressure, that's normal with some pumps. My AEM pump does the same thing. But in your case, it's probably because your pump isn't being triggered when cranking and the only fuel you're getting is at key on prime...

- Rob

 

Rob,
Thanks for the idea. The low voltage at the pump has been bugging me. It was on my list of things to investigate and see what the ideal should be. Could this be the issue even if a Noid light connected to the injector harness is flashing when I crank the engine? I have a battery charger attached to the battery almost permanently now given the amount of cranking and trying to start the truck I have been doing. Would this make-up for a poor battery or does the pump voltage really stand out to you as a problem regardless. I attached a datalog from today. I get a greater amount of partial ignition with the throttle partially open.
Ryan

 

Ryan, just watched your second datalog that you provided above and its the same issue. The ECM will only trigger the pump when it sees 400-RPM. That second datalog barely broke the 300-RPM mark. The Oil Pressure Sensor being an independent switch will also trigger the pump when it sees 4-psi, but this of course is based on the reliability of your sensor, plus at 300-RPM you might not be spinning it hard enough to see that oil pressure. Key on engine off will prime your rail and you "should" see pressure. The moment you crank that pressure is gone, and with no signal for the fuel pump the fuel pressure will of course read zero during cranking. As far as the injectors go, they are pulsing during cranking but with no fuel being prevalent in the rail due to you not seeing 400-RPM it obviously won't help...

- Rob

 

Ryan something for you to try.... go to your fuel pressure relay, and find the Red independent wire that we use for testing fuel pressure. Have a friend assist. Jump that Red wire to the positive battery terminal while someone cranks the engine, and see if she fires up. If it does, once she gets above 1000-RPM during cold starts, disconnect the wire and see if she stays running on her own.

- Rob

 

I have a fuel rail pressure gauge, my son said I have 42 consistently while cranking. Apologies if that got missed. Attached is a short video while cranking. You can hear it trying to catch and lots of firing but not exceeding much more than 300rpm.
Ryan

 

Okay that movie does help, but now it becomes the process of elimination. You're not seeing adequate RPM but you're saying you have 43-psi during cranking constantly w/out seeing 400-RPM? I have to assume the Oil Pressure Switch is barely triggering the pump during cranking. Does the engine "sound" slower as it cranks to you by any chance? If not, did you try switching your ignition control module yet, because Pin B tells the ECM your RPM and it may be skewed.

- Rob

Edit: I just seen you ordered new injectors from Southbay. That's a good investment on your part. You said earlier that your injectors ohm'ed okay, and you tested the connectors with a noid light and all were pulsing. If you didn't check all the connectors be sure you do because I seen you tested 1 & 3 but they are on the same bank so be sure to check the other side because one bank may be dead for all you know due to a bad ground. Difficult to point to the injectors as the culprit if that is the case, but either way new ones are a good investment. If you're worried the injectors are dumping fuel, lift the fuel rail and place the key in the On position and let it prime. You'll know immediately if they are dumping fuel. Not to mention your plugs would be saturated if they were. You also confirmed you're getting spark. The video confirms the engine is at least "trying" to catch, and it doesn't sound slow to me, so the engine is either flooded with fuel, or not getting enough. In my case, my mini starter cranks the engine very quickly during cranking, and I keep forgetting that the stock starters aren't as strong, and I'm not sure what kind of starter you're running so that may be normal for you. Again though, if your son confirmed fuel during cranking, but its not catching, and you're getting spark, then it's either too much fuel or too little. Remember that holding the pedal down all the way during cranking is flood mode, so it will clear any possible flooding on your part if need be. Best of luck to you...

- Rob

 

I think it is time to investigate the fuel pump voltage as you say Rob. I have replaced the injectors, oil pressure sensor and the ICM in addition to the fuel pressure regulator, pump, spark plugs, distributor, cap and rotor and coil. I ran a data log again afterwards. No real change. I can get it sputtering at 300 rpm but it won't catch. fuel pump voltage is about 10 volts through the attempt. I have datalog from today after putting everything back together. What should the pump voltage be in the WUD during cranking?
Ryan

 

I bypassed the computer control of the fuel pump direct from the battery. No change. Fuel pump was also seeing 40PSI while cranking.

 

Well, it is running after replacing the distributor and putting in a new battery. Started instantly which is a great feeling. The distributor was interesting in that I had already replaced the ICM, the pickup coil also tested within the Ohm range specified here. Not sure what was happening exactly.

 

Did you measure the pickup coil series resistance as well as resistance to ground? The insulation could have been breaking down.

 

I did not measure resistance to ground but I did notice that the green wire was oozing liquid and had corroded the terminals a bit. Sounds like what you are describing, the insulation breaking down.