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Discussion Starter · #1 ·
1999 suburban with 5.7 engine and roughly 265k miles. Started out simple- now no start. let me try and describe- this is long. Was having start issues at first- worse on colder days, almost to the point of not even starting. Coolant level was dropping regularly and getting worse with no apparent leak anywhere. Delphi fuel pump put in several years ago. Once it started ran fine.

Started with fuel pressure test - good around 58-60 psi, but noticed that largest rise in fuel pressure occurred to about 62 psi right after ignition was turned off--would bleed down after an hour or so to about around 40 psi. During this period, when starting ignition switch had to be o cycled off-on a number of times to start. Other than that it was running good. Thinking fuel pressure reg and intake manifold gasket might be the fuel and coolant issues.

Started tear down: had to remove lower intake and replace gasket, also installed new fuel press regulator, cleaned all parts put back in but had inadvertently put in parts of spider lines reversed front to back (6,8 and 5,7 reversed) so when I tried to startup , was really running bad, no power. Did some digging first found out that system is Central Sequential Fuel Injection (SCSI) so order is important. So pulled out top part and corrected spider positions on intake.

Put back together, started up still running rough, but perhaps a little better. Double and triple checked spark plug wiring and locations, all okay there. Checked to make sure all grounds and connectors in right places. Saw on posts that that cam to crank timing might be off but my scanner could not read cam retard to check. Found a way to reset, first by moving crank to TDC on compression stroke then setting distributor in correct orientation. Then started up using the “drill a few holes in an older distributor cap to set spark length to shortest spark trick” since I did not have an more expensive scanner. Turned the distributor to get to this point and it did run a bit better, but still had little power and was not smooth.

Next step, tried new spark plugs, no real change. Then pulled crank position sensor to look at and clean but did not think this would do much. Put it back after cleaning, and vehicle would not even start, noticed no signal getting to tachometer when cranking. Really started scratching my head to say the least. Decided to order new CPS (the kind with a short length of wires and connector) Part came in and I was apprehensive that this would fix anything. Changed CPS units, no change. Tested old part with power supply and looking at signal when metal was waved in front of it; part displayed good square wave output; it seems find. I started to look at wiring failure , so far have verified power and reference wiring, all good. Have not verified signal line yet. One question -- if signal fails to come from CPS, would this result in no signal going to the tachometer as well? Am thinking we may be looking at a wire failure that somehow occurred after removing CPS. Easy way to test?

When I cleaned the parts I believe I may have introduced some cleaning fluid with some contaminates in the Spider assembly fuel input so am thinking this could be the source of the rough running. Is there a way to check this? Am afraid that the best option may be to replace it with an MPFI aftermarket spider assembly.

your thoughts?
 

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Discussion Starter · #2 · (Edited)
1999 suburban with 5.7 engine and roughly 265k miles. Started out simple- now no start. let me try and describe- this is long. Was having start issues at first- worse on colder days, almost to the point of not even starting. Coolant level was dropping regularly and getting worse with no apparent leak anywhere. Delphi fuel pump put in several years ago. Once it started ran fine.

Started with fuel pressure test - good around 58-60 psi, but noticed that largest rise in fuel pressure occurred to about 62 psi right after ignition was turned off--would bleed down after an hour or so to about around 40 psi. During this period, when starting ignition switch had to be o cycled off-on a number of times to start. Other than that it was running good. Thinking fuel pressure reg and intake manifold gasket might be the fuel and coolant issues.

Started tear down: had to remove lower intake and replace gasket, also installed new fuel press regulator, cleaned all parts put back in but had inadvertently put in parts of spider lines reversed front to back (6,8 and 5,7 reversed) so when I tried to startup , was really running bad, no power. Did some digging first found out that system is Central Sequential Fuel Injection (SCSI) so order is important. So pulled out top part and corrected spider positions on intake.

Put back together, started up still running rough, but perhaps a little better. Double and triple checked spark plug wiring and locations, all okay there. Checked to make sure all grounds and connectors in right places. Saw on posts that that cam to crank timing might be off but my scanner could not read cam retard to check. Found a way to reset, first by moving crank to TDC on compression stroke then setting distributor in correct orientation. Then started up using the “drill a few holes in an older distributor cap to set spark length to shortest spark trick” since I did not have an more expensive scanner. Turned the distributor to get to this point and it did run a bit better, but still had little power and was not smooth.

Next step, tried new spark plugs, no real change. Then pulled crank position sensor to look at and clean but did not think this would do much. Put it back after cleaning, and vehicle would not even start, noticed no signal getting to tachometer when cranking. Really started scratching my head to say the least. Decided to order new CPS (the kind with a short length of wires and connector) Part came in and I was apprehensive that this would fix anything. Changed CPS units, no change. Tested old part with power supply and looking at signal when metal was waved in front of it; part displayed good square wave output; it seems find. I started to look at wiring failure , so far have verified power and reference wiring, all good. Have not verified signal line yet. One question -- if signal fails to come from CPS, would this result in no signal going to the tachometer as well? Am thinking we may be looking at a wire failure that somehow occurred after removing CPS. Easy way to test?

When I cleaned the parts I believe I may have introduced some cleaning fluid with some contaminates in the Spider assembly fuel input so am thinking this could be the source of the rough running. Is there a way to check this? Am afraid that the best option may be to replace it with an MPFI aftermarket spider assembly.

your thoughts?
 

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Discussion Starter · #3 ·
a few days ago, checked the fuel pressure again, running about 58 psi during crank about 60+ after ignition turned off.

today, tried the battery remove for an hour, to remove possible security lock, it did not remove security light on dash or let it try and start I'm at a loss on what to try - dynamite?
 
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