But this doesn't mean anything because the pathway for the reference pulse is still the culprit, eg; Ground circuits fail when Hot.

- Rob

 

under service manual and engine cranks but want start- chart A-2, it say ground diagnostic terminal, does light flash code 12? what are they wanting me to ground

 

Sigh... I didn't realize you weren't familiar with these systems, they want you to jumper A to B on the ALDL connector. A is ground, B is the diagnostic request line. When you ground B to A and turn the key ON, the ECM should flash code 12 three times. If it doesn’t flash 12, that means the ECM isn’t grounding properly, and this will tie directly into your hot no start w/code 33 issue. If you jump A to B and do not get code 12, then the ECM ground path is compromised.

- Rob

 

I didn't understand what they were telling/ I know how to jump a and b to get the codes.

 

The ALDL jumper test only gives useful information if it’s done when the engine is hot and in the no start condition. Doing it cold will always show normal behavior, so it won’t tell us anything about the failure. If you jumper A & B during the hot no start and the ECM doesn’t flash Code 12, that immediately tells us the ECM ground path is dropping out when the engine bay is heat‑soaked. That would explain the entire pattern you’ve been fighting. Since this was an engine swap, the next thing to confirm is whether the engine to body ground strap is installed and making good contact, along with the other grounds. A missing or weak strap can cause the ECM to lose its reference signals when hot. Also, when you checked injector pulse, was that during the hot no‑start or only when cold? If they’re pulsing hot, that rules out the old Multecs as the cause. I hear your frustration, but I'm trying to help you narrow this down so you’re not stuck replacing parts that aren’t the issue...

- Rob

 

It's not a "reference pulse" issue. FUGHEDDABOUDIT. A shot of starting fluid won't restore reference pulses. Not "intermittent" or any other kind of "reference pulse" issue. Your problem is NOT "reference pulses". Blee dat. Disabuse yourself of the whole dead end diversion from the path in search of shiny things.

See my signature for a helpful logical hint. Pay particular attention to the concept of "ALL" the facts. Which in this case, the established FACTS are: (a) your engine won't start if the cold-start injector doesn't help it; (b) it's a SWAP, so the chances of improper connection of SOMETHING are rife; and (c) adding starting fluid – FUEL – fixes the whole thing RIGHT UP.

The SYMPTOM is, won't start hot; the PROBLEM is, ECM isn't giving the right little startup shot of fuel. Simple. So simple even someone as stuuuupid as I can see it. See my signature.

D00d, it's JUST NOT THAT HARD. Put aside the "troubleshooting charts", and the "maybe it's this maybe it's that maybe the aliens have sent down their severest tester to determine the intelligence of this inferior race of cockroaches infesting this unfortunate interstellar cinder we found way out here around this piddly little ordinary star", and use some COMMON SENSE. See my signature.

You STILL have a problem (ahem, an "opportunity for a solution") wherein the ECM isn't aware that you've turned the key off and turned it back on again. Until you figure out why your ECM isn't seeing this simple sign of a "restart", you're gonna be chasing your tail indefinitely. Leave your tail alone and use some FORKING COMMON SENSE instead. See my signature.

 

Pretty sure he claimed he changed the ECM and prom as well, so the ECM is clearly responding to bad inputs, and, it doesn't get any easier than checking the Grounds. As for Occam, he stated not to multiply assumptions beyond necessity. To choose the explanation that accounts for all the facts with the fewest unsupported assumptions. A simpler explanation is that the ECM isn’t receiving the correct inputs to command fuel under that specific condition, which is exactly why he should be looking for reference signals, ignition feeds, and swap related wiring...

- Rob

 

Which is, THE ECM ISN'T SEEING THAT THE KEY HAS BEEN TURNED OFF AND BACK ON AGAIN.

Adding starting fluid doesn't restore "reference pulses". Which means then, that "reference pulses" CANNOT in any manner way shape form or fashion be the "problem". (ahem, "opportunity for a solution") They ARE NOT The Problem in this specific matter.

This is CORRECT. You are absolutely right. Leave out the "reference pulses", and William of Ockham is satisfied.

 

I mean it is right here, doesn't get any more simpler than this. When Multecs fail they do not stop the ECM from pulsing. No reference pulse when Hot points to Hi/LO reference dropping, he already said he replaced the ICM and pickup coil, but it could very well be a loose ICM Ground, or a bad connection at the 4-pin or 2-pin module plugs, or the reference wires are too close to heat. Could also be his Ignition feed voltage sagging during a hot restart, I mean what exactly is he reusing from his older vehicle from the fuse block as the injector wires rely on this wiring. The ECM Grounds could also be rising in resistance when Hot. I believe he already confirmed a working CTS. Engine runs fine whgen cold, not much else it could be especially after swapping ECM's and proms...

- Rob

 

Not that it really matters but he has swapped a 1988 L98 engine into his truck. He sent the original fuel injectors out to be refurbished.

RP Multec fuel injectors weren't used in TPI engines until 1989. No reputable place that services fuel injectors will touch the 1989 to 1992 RP Multech fuel injectors. They tell you to throw them into the trash where they all belong.

This being a engine swap I want nothing to do with the troubleshooting beyond sending him a link to a 1988 factory service manual and a video explaining the How, What, & Why these systems work. This type of troubleshooting is hard enough to do over the Internet not being able to see, hear, and touch things and it being an engine swap makes it even worse.

 

I want to thank everyone for all there help. my engine has a CSI and it fires during cranking process but not the other injectors until it starts, ii that what it is suppose to do? also how does a 1992 TPI fire without a CSI. The reason I'm asking is my 40 Chev has a 1990 TPI that don't have a CSI and after the 2 sec fuel pump it fires right up. trying to understand how the system works

 

I’m sure I’ve explained the csi operation on corvette form or here. So here goes again. The csi sprays fuel when craning only if timer switch is closed. Not ecm controlled. 89 maf uses cranking fuel and cold start enrichment logic same for tpi sd.

 

https://www.thirdgen.org/forums/tech...atic-only.html

same as the operation in the fsm

 

Watch the video I posted before in post #42.

GM Port Fuel Injection Training VHS by AVI - 80s / 90s How-To Tape

It explains everything you want to know about the Cold Start Injection system. Start at 26:38 and watch through 36:26. It explains how the 1985 to 1988 CSI system works and how 1989 to 1992 works without the CSI system.

 

by the sound of it TP, I think you are getting flustrated with me. I understand the switch controls the CSI or not. but what I'm asking is and you say thet is not ECM doesn't controlled csi or injectors but something has got to indicate whether the CSI fires or the other injectors and I'm assuming that on the speed densiity models and I assume again that the prom tells the injectors to fire when cranking. Please bear with me

 

I did watch it again. If I understand it by what he says is that it is programmed and I'm axxuming again that that would be in the prom

 

The 9th injector CSI system is 100% stand alone. The ECM doesn't even know it exists. If you took the entire CSI system off and threw it into the trash the ECM wouldn't know it was missing. There is no feedback or talking between them. Neither knows the other one is there.

On the 1989 and up TPI systems without CSI the ECM pulses the 8 injectors during cranking to add the extra cold start fuel needed to start the engine. The programming on the 1989 and up TPI systems is different from the 1988 and older systems.

 

👏

 

understood. whitch still leaves me with the no start when warm.I'm beginning to think it is un repairable

 

TP I don't know what that is and what it is suppose to mean

 

it’s a applause for a well said comment . Have you verified which a scanner the ecm is seeing crank pulse of 400 or higher when engine is warm? Kinda feel like you’re going in circles with 3 or more threads that answers are not given.

 

Of course it is repairable.

It starts and runs fine when cold. You have an intermittent problem that is based on temperature.

How long will it stay running after starting the truck when cold? Can it get up to full operating temperature and stay running without issues for a long time?

Does your truck have a tachometer? When you are cranking the engine when cold does the tach needle move and show RPM? If it does will it do it when the engine is warm and you try to start it and it doesn't start?

 

https://www.corvetteforum.com/forums...when-warm.html


https://www.corvetteforum.com/forums...ts-bypass.html

https://www.corvetteforum.com/forums...do-i-need.html

https://www.corvetteforum.com/forums...-when-hot.html

https://www.thirdgen.org/forums/engi...-starting.html

unfortunately that has been asked already

 

Are we still working on a problem wherein it doesn't start by itself butt a shot of starting fluid makes it start right up?

 

No TP I can't seem to find anyone that has a OBD1 scanner. I had one mechanic to tell me it would not do any good to use a scanner because it would not tell me anything. I live in a small town and machanics are very few without taking it to a dealershiip. can't afford there rates. I will keep looking for someone that has a OBD1 scanner and is knowledgeable of the L98 engine

 

Airwolfe. The truck will run as long as I let it run. I have drove the truck but when I return back to the shop it will not restart. when cold I can start the engine and let it run for just a minute or two and it will not start back. the temperature gauge will not even move. I suppose it is long enough for the coolent temp sender to change. I have no tach

 

I'm sorry TP if I ask the same questions but I have been on line to several sites for a long time trying to resolve this issue.I have check or changed everything that anyone has suggested

 

so the mechanic who doesn’t own the equipment to diagnose your no start says it wouldn’t help 😂 get a brick as mentioned before or load the parts cannon, ecm and updated tune.

 

And does adding a shot of starting fluid still make it start right up, like it did at the beginning of all this?

 

Post some pictures of the engine. I want to be able to clearly see the fuel injectors.


RP Multec Fuel Injectors

There has been too much assuming and guessing troubleshooting your problems. I assume you have a 1988 L98 engine and not a 1989+ L98 engine. I assume you sent out the stock injectors out to be serviced and that they are not Rochester Products Multec fuel injectors.

I'm done assuming and guessing. A picture tells a thousand words.

RP Multec fuel injectors are the Devil. They are retroactively defective by design. Little ugly hand grenades with the pins pulled so far out you just look at them the wrong way and BOOM. Even if they test good they are bad. All of them are bad.

They will make you chase your tail around in circles and pull your hair out by the roots.

The flowchart for troubleshooting them is #1 Open hood and look at the fuel injectors, #2 Are they RP Multecs, If YES then throw all 8 of them into the trash can and replace with brand new Delphi fuel injectors, If NO then keep troubleshooting the problem.

These little MFers love to run good when cold but when they get warm or hot that's when the nightmare party starts.

 

Never mentioned if this was a cold or hot ohm reading.

Quote:

Originally Posted by snackstick

I had the factory Injectors that came with the engine rebuilt, not sure what # they are. I ran a resistance check a while back and they were 16.1 to 16.3. I will check them again. I also have purchased a adjustable fuel regulator and will get it installed within a few days. Thank you

 

 

Here TP,

 

can anyone recommend a OBD1 live data scanner that won't break the bank.

 

OK. Those aren't RP Multecs. So the problems isn't RP Multec fuel injectors.

 

What do you consider not breaking the bank?

I have plenty of Snap-on MT2500 Scanners in perfect condition and Primary and Fast Track Troubleshooter cartridges for them too.


Snap-on MT2500 Scanner hardware version 1.8 without backlit screen.


1980.5 to 1993 GM Primary Cartridge with thru 1993 US Domestic Fast Track Troubleshooter Cartridge.

Above is the minimum you will need for a Snap-on MT2500 Scanner with the Primary & Fast Track Troubleshooter cartridges to diagnose your car or truck or whatever it is you have with a 1988 L98 engine. Also it would come with the Snap-on data cable and the Snap-on GM-1 OBD-I adapter you will need and a Snap-on 12 VDC battery power cable you need to plug into the Snap-on GM-1 OBD-I adapter. GM's 12 pin ALCL/ALDL (OBD-I) diagnostic port doesn't supply positive 12 VDC power.

It won't come with a Snap-on 12 VDC cigarette lighter power adapter if you just get the GM Primary cartridge because the Snap-on one loves to self eject from every single GM cigarette lighter/power outlet I've ever plugged one into. I wouldn't subject anyone to that bullshit. It sounds just like a M1 Garand ejecting the clip after firing the 8th round of ammo. Also you will run into vehicles that don't have a working cigarette lighter/power socket more often than you would think.

What all cars, SUVs, and trucks do you have? Year, make, and model. Plus stuff you have engine swapped and with what year, make, and model engine?


1983 to 1993 Chrysler Primary Cartridge with thru 1993 US Domestic Fast Track Troubleshooter Cartridge.

1981 to 1993 Ford Primary Cartridge with thru 1993 US Domestic Fast Track Troubleshooter Cartridge.

Thru 1999 4 in 1 US Domestic Primary Cartridge with thru 1999 4 in 1 US Domestic Fast Track Troubleshooter Cartridge. The JEEP coverage starts at 1984.

Example of US Domestic ODB-I & ODB-II Reference Manuals & Generic OBD-II Reference Manuals.

 

How to use the Snap-on MT2500 Scanner.

 

I have priced used snap on scanners and the cheapest one I found was $500. I probably won't use it only on this project

 

Look on fb marketplace and eBay, I picked up a graphing one with cables and cartridges for $175

 

Just a few quick searches you should be able to find one for $150-250 range

 

where were these listed at? ebay? I'm interested in one

 

Fb marketplace

 

SOFAKINGDOM what are you talking about when you say see my signature

 

Numquam ponenda est pluralitas sine necessitate.
— William of Ockham, c. 1330 AD, from Quaestiones et decisiones in quattuor libros Sententiarum Petri Lombardi

Roughly paraphrased into modern English, and applied to figuring out what's wrong with your car:

The simplest explanation that fits all the facts is most likely to be the right one.

 

That's a paraphrase of the logical saying commonly known as Occam's Razor. "Occam" is a misspelling of the town that Wiliam of Ockham was from. The saying is a logical "razor": a mental method of trimming away all the BS and getting down to what matters. Ockham's actual Latin words mean "Plurality [number of entities] is not to be multiplied without need". He was talking about another matter entirely in which "intellectual" people at the time would get all wound up in BS and complexity trying to logically "prove" a particular thing they were interested in, not fixing cars, which if you read Peter Lombard you can see what it was, butt it's not material to the matter at hand.

In inductive (probability related) and abductive (reasoning from incomplete information), both of which forms of logic are applicable to fixing a broken car, this means gathering whatever facts are available, and proposing "explanations" to account for them. Such as in troubleshooting a car that's misbehaving, and reasoning toward what needs to be fixed. This "razor" is a quick and dirty way to eliminate some of them sometimes. It's no guarantee of correctness, butt it's a guide to throwing away BS "explanations" at least initially, and leading toward the highest probability one(s) among any/all that are proposed. Every word in it is important to its meaning.

Simplest = the fewest, most common, and most likely "moving parts"; for example, invoking alien abduction as your "explanation" is ... yeah. Butt also, convoluted structures that require multiple things to fail just precisely so and to then suddenly and inexplicably repair themselves without being touched are not "simple"; "explanations" that require many "moving parts" (the so-and-so is broken just this way, and the such-and-such doesn't quite touch until vibrated, and the ... all of which are required to make the "explanation" complete) are not as "simple" as ones that require only one broken thing (the wire is disconnected or something uncomplicated and common like that) ; and so on. The point of that word is, "explanations" that are more "simple" are preferred over ones that are less "simple", until demonstrated otherwise.

Explanation = we're looking at something(s) happening, and trying to figure out the "why" for it. Each proposed "this is why it's doing this" answer is an "explanation".

Fits = the "explanation" must match the observations. For example, if your proposed "explanation" involved bad spark plugs, then that "explanation" must "fit" everything you know about this; which it wouldn't, because spark plugs don't magically repair themselves by squirting starting fluid into the intake. Which is NOT to say, your spark plugs are good; only, that you can change them every day, and twice on Sundays just for good measure, and you will NEVER fix the problem at hand by doing so.

All = means just what it says. ALL of whatever observations you have made, must be accounted for by a proposed "explanation" in order for it to be true. If ANY observations are left unaccounted for, then the "explanation" is incomplete at best, and more likely, wrong.

Facts = the things that are happening. Does it start? What is the voltage here or there? Does it start if I shoot starting fluid into it? Does it not start if I don't? These are "facts". A proposed "explanation" must "fit" "all" "the facts".

Most likely = the simplest explanation MAY NOT be the "right" one, butt more complex ones are progressively even less likely to be "right", as their complexity (lack of being "simple") increases. This means that the "simplest" "explanation" is where you should start looking. If one or another proposed "explanation" is more "simple" than others, devise tests or measurements or observations that might either confirm or falsify that one, FIRST. The "simplest" isn't "always" right; just, more often than not, by far. This avoids or at least minimizes tail-chasing and endless rounds of "maybe it's this maybe it's that". Not that any of that ever happens, of course.

The right one = you just zeroed in on the broken thing you need to fix.


So: in your case, the facts are pretty straightforward. Let's list them.
-

1. The engine starts up fine when "cold". Not entirely sure what that means in your case; whether it's San Diego "cold" (60° F) or Yellowknife "cold" (-35° C), or just after it sits overnight, or what; butt we'll just leave it at "cold" for the moment.
2. The engine doesn't start on its own when not "cold".
3. The engine starts when not "cold" by shooting starting fluid into the intake.

Those are enough "facts" to be able to eliminate MANY proposed "explanations", so now let's look at some of those.

Reference pulses - ANYTHING to do with them - will they disappear when an engine is not "cold" (you have repeatedly told us that this doesn't mean "hot" which would be a critical "fact" if true, butt just, "not cold"), and instantly reappear without leaving a trace of their disappearance, by shooting starting fluid into the intake? NO. Clearly this can't happen. Therefore we can ELIMINATE any and all "explanations" involving them from consideration.

ECM - ANYTHIING to do with it - same logical test. Will shooting starting fluid into the intake repair it? NO. Clearly this is not a "fact". Therefore we can ELIMINATE any and all "explanations" involving that from consideration.

"Scanning" - rather than repeating myself, see the above 2 "explanations" and their rebuttal.

And so on and so forth. You have 3 very simple "facts", and ANY "explanation" that will lead to the source of the problem, MUST fit them "all". ANY "explanation" that DOESN'T fit them "all", CANNOT be "the right one". That is, if some one or another of the "facts" differs from whatever an "explanation" would predict, then that "explanation" is WRONG.

Does this make sense?

Fact #3 is telling you that there is no fuel being delivered under the conditions in question. To Tuned's point, the injectors don't begin firing in the pattern of the engine "running", until engine RPM reaches a few hundred RPM; butt the starter is LUCKY to break 100 RPM. The injectors will NEVER fire based on spinning the engine with the starter. They get fired on ANOTHER basis for startups, which is, the ECM recognizes that the driver is about to try to start the engine, and in preparation for this, commands them to deliver a shot of fuel, designed to be enough to last until the engine starts and reaches sufficient RPMs for normal processes to take over. Fact #3 is telling you, YOU DON'T GET THAT SHOT OF FUEL AT THAT TIME unless the engine is "cold", therefore you have to deliver it by hand, which then allows the rest of the process to operate as if normal. The question then is, why aren't you getting that shot of fuel? The only really possible answer, or at least, most certainly the "simplest", is that the ECM doesn't know that the engine was turned off and back on again, therefore doesn't prepare for a start.

Capisce?

 

Capisce, so why does the ECM not know that I switched off and back on. and how do I test to find out why

 

I kinda think that's where we all started out.

It'll be in the wiring somewhere. This being a swap, there's plenty of opportunities for that. Like a good friend of mine years and years ago, mid 70s, that had an old Chevy truck (64 or so IIRC) that was born with a 6-cyl in it, and he had put in a 327, butt the old motor had been yanked and all the wiring for it was gone when he got it as a roller. So he went digging under the dash looking for a wire "that was hot with the key On" to hook up to the coil (back in the points days, before electronic ignition). Somebody had also put in an underdash AC unit and left a ginormous bird's nest of about 300' of wire under there and that's where the wire he found was, and he never tracked it back to see where it came from, or anything. It had trouble starting after he got the new motor in, butt he figured out how to do it: whirl it over with the starter, pump the gas after a second or 2, and let off the key with the throttle held open a little, and it would fire RIGHT UP; then it was perfect once it got running. If OTOH you just turned the key to Start and let it whirl, it would just run the battery down. He got so used to it, it was 2nd nature. He later sold it to a mutual friend, who didn't know about that, and it left him stranded several times, and asked me for help straightening it out one weekend. Turns out, the wire in question wasn't hot in Start, so as long as the truck was trying to start, the ignition system had no power, and it would NEVER fire; not until you let the key off. Easy enough to fix butt maddening to somebody that didn't know about it.

I suspect yours is something a bit like that. I'd start by looking at EVERY SINGLE wire going to the ECM, besides sensors and injectors and such; and see what voltages are on which ones when. Make a table: it would look something like, pin 1 has 12V at all times; pin 2 has 12V in Run only; pin 3 has 12V in Run and Start; pin 4 is the O2 sensor so I don't care about that one; and so on. Maybe even, get a copy of the FSM for whatever year TPI you have (88? I forget) so that you have the COMPLETE schematic of THE WHOLE CAR. That way you'll have all the info that there is about what's hooked up how from the factory.

 

I think I have a ** GM schematic. I will double check but I'm pretty sure I pulled the 12v off the fuse block that had 12v. all the painless wiring was labeled so if it's wrong it on there end.
I wan to add that when warm or hot the first time restarting it allways fires one time or tries to start. after the first time it don't make any difference how many times I try it won't hit

 

The schematic is located in the pdf on your thread. The pinout I posted on cf, 2 constant hots B1.C16 and one switched power a6. High tps reading, shorted injector coils, ecm not seeing drp because it’s bad or reference wire or icm has an issue. All possible causes no injector pulse engine warm.

 

Unless you add fuel, right?

As in, whatever little bit of fuel that happened to be left in the intake when it was last shut off, there's a molecule or 2 left, enough to puff a cyl or 2, and that's all? Butt add a shot of fuel to replicate the one that the ECM doesn't command, and it's back in business like nothing ever happened?

Of course when the engine is "cold", whatever the exact criteria the CSI uses for its operation might be, THAT supplies enough fuel so that the other makes no difference.

I didn't realize you hadn't seen this site on a computer. It's an ALTOGETHER better experience than on a phone. WWWWWAAAAAAAAYYYYYYYYY too much info gets cut off in the phone version of this software.