1987 v30 Chevy hard starting

[ksalt]

Hi I have been working on on an 87 Chevy  and am having a problem with it hard starting all of a sudden.  It will turn over and then eventually try to start and sputter. If I'm lucky to get  it to start it idles in the 1700s.
I have checked the ecm connection as well as only get the 12 code. I looked at the injectors did the check unplugged  them no spray plugged  in they spray. Pulled the plugs found one cracked one but the rest will through a  spark a 1/2in spacing. The cap rotor and wires and plugs are new just have been sitting  for a while. I thought  I got bad gas but even with starting  fluid  it doesn't  change.  Anyone  have thought on what to check next thanks.

[VileZambonie]

Check your fuel pressure

[ksalt]

I finally got the  adapter for the  fuel line and with the key on its at about 8 psi and the truck started it was at 12 psi. It idled at about 1000 kinda had little lope maybe  timing is off. And service light  was on. Wouldn't  restart and no new codes.

[ksalt]

Got a little  further on the truck I can get it to start after its been running some. At some point  someone added a second catalytic converter and i took it off. so I'm guessing that the old one is bad and they did just a quick  fix. Service light still stays on and has a ruff idle but it's down to 700 now.

[MIKE S]

If the cat was near the rear it was probably stock. Had several 1 ton cab and chassis we bought new in 87. All had a front cat and another near rear of truck. Probably a California thing.

[frotosride]

If the SEL is still on check for codes again, remember that the ECM will always do code 12 first then repeat the actual code over and over. A few things to check that may be helpful:
1: Timing- remember to disconnect the set timing connector. Timing should be 0* TDC unless it's a 454 then it's 4* BTDC. I've never had a problem setting the timing to the OE setting along with verifying idle speed(connect a tach and leave it under the hood so you can watch everything at once). You shouldn't have to adjust the idle screw, but often the IAC Pentel gets gunked up or sometimes just needs to be reset and rarely replaced.
2: ensure the EGR is functioning properly. Remember it isn't always sending exhaust into the intake but when it does the ECM changes timing.
3: ECM coolant temp sensor. If is is bad or going bad it can cause a lot of issues from rough idle, backfiring, stalling and no start when engine is warm. The sensor screws into the intake manifold, on the front passenger side, by the thermostat housing. It's a two wire connection. ACDelco is what I would recommend to replace it with but they no longer make them. I have had great success with Standard brand.

To test the coolant sensor, unplug the wire connector and test the resistance across the two terminals of the SENSOR with an ohm meter.

Coolant sensor approximate resistance specifications:
177 ohms @ 212 deg. F. or 100 deg. C.
241 ohms @ 194 deg. F. or 90 deg. C.
332 ohms @ 176 deg. F. or 80 deg. C.
467 ohms @ 158 deg. F. or 70 deg. C.
667 ohms @ 140 deg. F. or 60 deg. C.
973 ohms @ 122 deg. F. or 50 deg. C.
1188 ohms @ 113 deg. F. or45 deg. C.
1459 ohms @ 104 deg. F. or 40 deg. C.
1802 ohms @ 95 deg. F. or 35 deg. C.
2238 ohms @ 86 deg. F. or 30 deg. C.
2796 ohms @ 77 deg. F. or 25 deg. C.
3520 ohms @ 68 deg. F. or 20 deg. C.
4450 ohms @ 59 deg. F. or 15 deg. C.
5670 ohms @ 50 deg. F. or 10 deg. C.
7280 ohms @ 41 deg. F. or 5 deg. C.
9420 ohms @ 32 deg. F. or 0 deg. C.
12300 ohms @ 23 deg. F. or -5 deg. C.
16180 ohms @ 14 deg. F. or -10 deg. C.
21450 ohms @ 5 deg. F. or -15 deg. C.
28680 ohms @ -4 deg. F. or -20 deg. C.
52700 ohms @ -22 deg. F. or -30 deg. C.
100700 ohms @ -40 deg. F. or - 40 deg. C.

[ksalt]

The cats one was a old original  and a new honeycomb one. The egr was Clean and held vacuum when I tested it. I checked the coil it test at 7 and 11k.  the temp gage works but will check it and cleaned the oil pressure  one and it started reading pressure . It's a 454 and have it set at 4 degrees.
 This morning I went out to work on it and do not seem to be getting  spark out of the coil. Hard to tell for sure  by myself . It is getting 12v with the switch  on. I tried a  replacement  icm but think it was bad.

[frotosride]

If you don't want to buy or make a remote starter (it's very simple) you can pull #1 plug wire or #2 because they are bothe long. Place it on the cap wherever you want or if you just want to test the coil for now place it on the coil. Get a spark plug in the other end and find a spare piece of wire. Wrap the wire around the threads of the plug and ground the other end.  Now you can simply put the wire under your windshield wiper to hold it in place as you bump it over. Recommend disabling your fuel pump though.

For the CAT it likely wasn't making emissions so they put another on it. Problem, if the OE CAT is still in place it can be clogged, it doesn't have to be completely clogged to cause a problems, the main issue with that is typically they are welded especially in states that really care. For diagnostic purposes, remove the mid pipe and see what happens.

[ksalt]

I replaced the  coolant sensor the old one didn't get  any reading the neway one had 1800 or somthing. Is the wiring  harness supposed to have 1200 ohms? But Still have a no spark issue. I have remote starts just have not disconnected the cluck safety switch to make it work.
.

[frotosride]

1200ohms would suggest that is gas close to 100* outside when you tested it so call that one good!
Never measured resistance across the ECM but considering that the ECM sends power out to several functions, IAC, TPS etc and collects resistance on the return, not surprised to see that kind of resistance. Either way it isn't stopping your spark.

So if you have power to the coil these next steps are going to be difficult without the remote start. If you put the truck in neutral to keep it from running away and embarked on you can hook straight to the solenoid and bypass all the safety's! Just be safe

First use a meter or simple light probe and back probe power to the coil right at the plug. With ignition on you should still have battery voltage (verify this first). Now turn the engine over to make sure you still have coil power while cranking.

If power to coil is strong minus what you see from starter surging, then move on to testing ground control (ICM). Back probe the ground wire for the primary coil while cranking. Easiest way for this is with a test light or peak capture on a multimeter. What you want to see is the light flicker or on the multimeter you want to see the break in resistance. It should be rather consistant.
If both of these check out it is likely your coil, cheap fix.
To verify this test resistance from ground control to power in() you should have at least little resistance less than 1 ohm or so this is primary coil. Then do the test resistance from the ground control side to the output of the secondary(coil plug)should be a small resistance change. If you have high resistance or none then the primary coil is likely burnt and or grounded.

*** Don't forget to test the resistance of you probe wires befor doing any resistance check***

[frotosride]

I'm going to look for a good video to help you with this...

[frotosride]

This one uses the simplest tools to do some basic troubleshooting and then shows you with an scope that your findings were right...enjoy!



https://www.youtube.com/watch?v=mDKj19Hnhd0

[ksalt]

I'm guessing  the pickup coil is bad didn't get any positive pulse and only .2 ac volts off of it. So a new distributor should  fix it.