91'capriceclassic-no start!

[Mr.Rivera]

I replaced the fuelpump and the sending unit on my Caprice Classic-(Gas gauge stuck on 3/4 of a tank) Installed everything back together correctly. Fuel spits out when i crack the fuel lines on the throttle body(so I now I have fuel pressure) but not @ the 2 injectors. I replaced the fuel pressure regulator inside the TBI, still no fuel spaying out(injectors) I also put a test light to the plug-ins on the injectors and have fire, I dont know what to do next, Im stuck.

[kdrolt]

Are the injectors pulsing? How do you know that they aren't?

The injector circuit can be tested for electrical pulsing using a test lamp (called a "noid" lamp) to see if the injectors are being pulsed by the ECM:

http://cgi.ebay.com/ebaymotors/1987-...spagenameZWDVW

Have you used the paper clip trick to see if there are any engine trouble codes being set? I'll let you do a search on the web for the directions..... in short you don't need a scan tool, you just need a paper clip to run this diagnostic test.

Failure to start, assuming nothing mechanical is toast, is always fuel or ignition related. You need to walk down the troubleshooting steps for both.

[Mr.Rivera]

I have to special order the NOID test light, be here friday. I made a jumper wire and code fashes 12,34- 3x each. I dont have a manual on this vehical. Any idea what these codes mean?

[kdrolt]

In general:
http://www.troublecodes.net/GM/

for your VIN code 7 (350, 5.7 copcar engine)
http://www.troublecodes.net/GM/91_577_tbi.shtml

12 means a diagnostic mode per the very bottom of this page:
http://www.troublecodes.net/GM/

which is a diagnostic to tell you that diagnostic mode has started (i.e. it's not a trouble code at all)

and

34 means "MAP sensor signal voltage was too low (high vacuum) when engine speed was under 1200 RPM or the engine speed was over 1200 RPM with a throttle position angle above 21%."

MAP = manifold absolute pressure, from the MAP sensor which is, I think, attached to the firewall on a 91-93 Bcar.

Remember that the injectors will only deliver the fuel for a particular engine rpm, coolant temp, throttle position, and engine vacuum (to sense load on the car).... and all of that comes from a look-up table stored in the ECM (in the PROM chip).

If the sensors that feed the ECM are defective, i.e. from

1. the engine rpm pickup inside the distributor,
2. the coolant temp sensor (CTS, mounted in the intake manifold),
3. the throttle position sensor (TPS, mounted on the TBI body),
4. the MAP (manifold absolute pressure, on the firewall but hose-connected to the intake)

and to a lesser degree the

5. the IAT (intake air temp) sensor mounted on the factory air cleaner back-half

then the ECM will command the injectors to deliver the wrong amount of fuel, and the car will either run rich (failed CTS sensor), too lean (vacuum leak somewhere, defective MAP, or broken vacuum line/hose somewhere)... or maybe not at all.

Note that I'm not listing all the possible failure modes because you might have more than one.... that's why there are troubleshooting charts in the FSM to work through to get to the problem quickly.

[Mr.Rivera]

I appreaciate all the advice you given me so far, What voltage %age am I looking for to chech the pick-up coil and ingnition coil?

[kdrolt]

Remove one spark plug, and then re-attach the wire to it. Position the plug so that the threads are in contact with the car body (ground path) and then have someone crank the engine. Do you see that (removed) plug firing (do you see a spark jumping the gap?). If you do, and if the timing is set properly then you should have enough spark to fire the engine, which means the coil and pickup are at least functional.

You said you tested the injector connector with a light suggesting that they are being pulsed, but no fuel comes out. That's hard to believe that you would have zero fuel from either injector. The odds that both are clogged is small.... unless the car sat unused for a very long time. If so, then the pintle valve at the lower tip of each injector is probably gummed/stuck closed.

Take a small can (tuna, cleaned) and pour injector cleaner into it and then try to maneouver it under an injector (one at a time) so that the injector tip is submerged in the cleaner. A bettter way to do this is to remove each injector and let them soak vertically with the tip-ONLY immersed in the fluid.

[Mr.Rivera]

I went out yesterday and purchased me a Chilton manual for this vehical. I know that I have a fuel and ignition problem. I have light but no pulse at the injector clip anymore. I went step by step in troubleshooting and got stumped. My fuse box #11 & #16 are 7.5amp fuses, as well in the book(diagram). what gets me is that on page 6-47, the schematic for my 91'- fuse #16 shows to be a 20amp fuse and hot at all times(I have no test light power @ this connector. Now theres a misprint in this manual. I know that the injectors run off of one of these 7.5 amp fuses. I have power to injectors-(fuse#11) What does fuse 16 operate???- Is it the ECM fuse???

[Blue Bowtie]

The horn.

[Mr.Rivera]

Well the pick-up coil (Chilltons manual- told me that the ohms should read 500 to 1500) my $500 dollar Snap-on multimeter showed it to be reading 1300 ohms, So I know it was in specs!! Now I was @ a holt!!! Everything read on the diag. showed to be good(Chiltons). I had no idea why there was no pulsation at the injectors as well as no spark when everthing cheched out to be good!! So I had no choise to have my baby(91' Caprice) towed to a shop to put it on their computer! They told me that there's 2 ways to check the pick-up coil, voltage in and out WTF?!?!?!? The manual said nothing about that!!!! What a waste of $30!! I had it towed back and I did disassembled the dist. and fixed the problem!! I wanna thank Kdrolt and Blue Bowtie for the help and advise!! These GENTLEMAN know there shit!!!